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As it happened: Saturday practice
By Geoff Creighton and Emlyn Hughes
The live commentary has ended. No further updates will be posted.
Vettel14:55 Hello everyone and welcome to AUTOSPORT Live for day two of action from the United States Grand Prix. This is the penultimate round of the 2012 FIA Formula 1 world championship and the battle is on between points leader Sebastian Vettel and his challenger Fernando Alonso.

It was the German who took early control at the brand new 5.513km Circuit of the Americas yesterday, but he faced lengthy car repairs in the afternoon, losing important track time due to a water system failure.

The Red Bull mechanics did a great job of fixing his car and he duly went out and topped the timesheet on medium compound tyres with a lap of 1m37.718s. His lap was 0.757s clear of team-mate Mark Webber, with Alonso third and Lewis Hamilton in fourth spot.

Vettel quickest in second practice despite problems

The teams now have just 60 minutes to finalise their set-ups and complete preparations for qualifying and tomorrow's 56-lap race.

14:56 Conditions are fine and dry but again on the cold side this morning. But it should warm up - both on track and in the air - with a maximum reaching 21 Celsius later this afternoon, while a light south-easterly breeze will give the drivers and race engineers something to think about.

Tyres14:57 Pirelli's medium and hard compound tyres are the talk of the paddock this weekend, with the hardest possible allocation appearing to be a conservative selection for the super-smooth Austin asphalt.

Drivers struggled to generate heat in both compounds yesterday, with the best laptimes arriving deep into a long run - not the ideal way to use tyres in qualifying.

Teams will hope further rubber goes down on the racing line, but with limited tyre wear and a track surface that is still very slippery, grip levels could remain at a premium all weekend.

Pirelli defends tyre selection

14:57 The fans are out in force again, with a strong crowd on hand at this early hour in Austin.

14:58 Race engines and gearboxes as ever fitted to the cars last night, with an installation check first thing on the job list this morning.

14:59 Karthikeyan is advised that the wind is quite low and that track temperature is 15 degrees, with a couple of minutes to go.

0 min: Final practice is underway.

0 min: Kobayashi is the first man out this morning in his Sauber.

0 min: Karthikeyan joins the Sauber duo on track, followed by di Resta in the Force India.

1 min: Maldonado also heads out early to check the condition of his car in the chill morning air.

1 min: Button and Hamilton head out, as does Massa in his Ferrari.

1 min: Hulkenberg joins the racetrack, with Senna coming out a few seconds later.

2 min: The early runners are back into the pits at the end of their installation lap, as Vettel heads out.

3 min: No move as yet from the Mercedes or Toro Rosso drivers.

3 min: Raikkonen joins the circuit in his Lotus, while championship challenger Alonso is also on his first lap of the day.

4 min: Webber, de la Rosa and Vergne are on the circuit to check the condition of their cars.

4 min: Grosjean has managed to exit at Turn 19 on his first lap of the day and was followed off the road by Glock in the Marussia.

4 min: Massa has continued on to a second lap, as has Hamilton.

5 min: Ricciardo, Rosberg and Schumacher are the last to head out for an exploratory lap.

6 min: Vergne crosses the line and begins a second tour in his Toro Rosso.

6 min: Hamilton ends his early outing and heads back to the McLaren garage for checks.

6 min: Ricciardo and Rosberg similarly begin a second lap - the latter weaving vigorously across the line to try and generate heat into his tyres.

6 min: Raikkonen has continued for a second lap, collecting some aerodynamic data on Lotus developments.

7 min: It's a 1m39.107s for Raikkonen as he completes the first timed lap of the day.

7 min: Vergne is quicker than Raikkonen with a time of 1m47.839s.

8 min: Ricciardo also completes a timed lap and comes through in 1m48.955s to go into an early second spot.

8 min: Rosberg completes a slow tour of the circuit and breaks the beam in 1m52.636s.

8 min: Schumacher is also working through a building run and he crosses the line at the end of his first timed lap in 1m55.044s.

9 min: Vergne lowers his time by over four seconds with an effort of 1m43.593s.

9 min: Plenty of concern from the engineers about this morning's low temperatures, with the potential for graining tyres as they struggle for grip.

9 min: Ricciardo comes through at the completion of his second timed lap in 1m44.173s.

10 min: Rosberg also completes a second effort and moves to the front with 1m43.300s.

10 min: Schumacher is next over the line and he takes over with 1m42.396s.

10 min: Vergne retakes the top position as the drivers continue to build up speed - 1m41.546s.

11 min: Ricciardo slots into second spot behind his team-mate with a lap of 1m42.035s.

11 min: Rosberg retakes the top position when he comes over the line - 1m40.745s.

11 min: Kobayashi and Perez are warming up towards an early run in the Saubers.

12 min: Before Schumacher moves to the front with 1m40.580s - despite his seat belts digging into his left shoulder.

12 min: Vergne cannot repeat the cycle this time. He goes 0.005s slower than Schumacher with 1m40.585s.

13 min: Ricciardo improves with a time of 1m40.872s but he remains in fourth position.

13 min: Rosberg improves with a lap of 1m40.745s but that only places him third on this occasion.

14 min: Schumacher improves again with a lap of 1m39.483s and takes the gap out to 0.518s over Vergne.

14 min: Massa joins the circuit for his first run on the hard tyres.

15 min: Rosberg comes round for another lap and moves to the front, ahead of team-mate Schumacher with a time of 1m38.589s.

15 min: Schumacher returns to the pits at the end of a six lap run in the Mercedes. He remains in second for now.

16 min: Vergne registers a slight improvement with 1m39.689s. He remains in third position.

16 min: Perez is up to fifth fastest after his early efforts and is told by the team to use DRS earlier out of Turn 1.

16 min: Rosberg lowers the benchmark with 1m38.221s, putting 0.435s between himself and team-mate Schumacher.

17 min: Karthikeyan has joined the circuit to begin work after the installation lap.

17 min: Vergne has ventured off the road at the popular tourist spot at Turn 19. He continued.

17 min: Kobayashi springs up to second fastest with a 1m38.656s effort in his Sauber.

18 min: Vergne comes into the pits just after rejoining the circuit. He is fourth in the classification.

19 min: Rosberg is back into the pits after completing an eight lap run. He remains quickest with 1m38.221s so far.

19 min: Perez joins his team-mate in the early top three as he clocks 1m39.192s, while also topping the first sector on his next lap.

20 min: Karthikeyan joins the party with a lap of 1m50.956s. He is eighth in the standings.

20 min: Oh dear... contact on the track between Perez and Pic, with the Mexican going for a closing door and spearing the Marussia.

21 min: Di Resta, Maldonado, Hulkenberg, Senna and de la Rosa are now on the circuit for a first run since the installation lap.

21 min: Perez is now touring back to the pits for checks, while Pic is also still mobile but the stewards may be interested in that incident.

22 min: Karthikeyan lowers his time to 1m48.666s, but the Indian has slipped down the pecking order to ninth position.

22 min: Perez appeared to be overly-aggressive in looking for track position while on a quick lap, with the Mexican getting a reprimand yesterday.

22 min: Hulkenberg posts a slow 1m49.520s lap as he builds up speed in the Force India.

23 min: Meanwhile, Button has joined the timesheets in eighth, with team-mate Hamilton 10th after early laps on hards.

24 min: Hulkenberg comes through for a second timed lap and moves up to ninth with 1m43.936s.

24 min: Button has more temperature in his tyres now as he clocks a 1m38.583s to go second fastest.

24 min: Vettel joins the racetrack, followed by team-mate Webber a few seconds later.

25 min: Hamilton is also moving up the order, going sixth fastest with his latest effort.

25 min: Schumacher comes out to begin his second run in the Mercedes. He is currently fifth in the classification.

25 min: Rosberg tops the list with a time of 1m38.221s, with Button second, Kobayashi third, Perez fourth and Schumacher fifth.

26 min: Hamilton is told of problems with the brake temperature sensors on his Mclaren and is asked to ignore warnings from the electronics.

26 min: Di Resta improves his time with a lap of 1m41.435s and the Scot is up to 10th, but there are quicker drivers still to post a time.

27 min: Maldonado takes 10th away from di Resta with a time of 1m41.048s.

27 min: Webber and Vettel are midway through their first timed lap of the day.

27 min: Button goes one better to take the benchmark in 1m37.973s.

28 min: Webber joins the fun in 12th position with a first effort of 1m40.719s.

28 min: Hamilton is now the quickest man in the middle part of the lap, moving up to fourth fastest.

29 min: Vettel is down in 17th after his first timed lap - 1m43.387s - but a slow start from the Red Bull drivers is nothing new.

29 min: Grosjean comes around in 1m38.753s to take fourth away from Hamilton and is also now fastest through the flowing first sector.

29 min: Vettel improves to 14th with 1m40.838s as he continues to build up speed.

30 min: Webber is a little further up the standings. He is into 11th with 1m39.950s.

30 min: Pic returned to the Marussia garage after being assaulted by Perez and remains there while the team check over the car.

31 min: Maldonado has climbed up the classification to third spot, behind Button and Rosberg, with a time of 1m38.600s.

31 min: Button improves the time to beat with a 1m37.659s as he continues to find pace in ever-warming hard tyres.

31 min: Schumacher, Vergne and Ricciardo are all on the circuit using Pirelli's medium compound tyre.

32 min: Little action so far at Ferrari, with the team practicing stops on single laps in and out of the pits.

32 min: Schumacher moves up the order to sixth spot with 1m38.725s.

33 min: Vettel is beginning to get on with it as he crosses the line in 1m38.034s. That gets the German into third spot.

33 min: Button continues his progress with a new best of 1m37.538s Team-mate Hamilton is up to second but told he is losing time in the first sector

34 min: Schumacher improves again on his medium tyres and is fourth with 1m38.078s, just ahead of team-mate Rosberg.

34 min: Both Ferraris on track now with hard tyres fitted and the pair may finally be getting on with a timed run.

35 min: Hamilton betters his times through all three sectors to top the ever-improving times in 1m37.492s.

35 min: Webber continues his slow improvement up the ranks. He moves into sixth spot with a time of 1m38.402s.

36 min: Vergne has stopped to the side of the track with deranged suspension.

36 min: Both front wheels are pointing inwards and the yellow flags are out, hindering other drivers' attempts to improve.

37 min: Replays offer little explanation as we see Vergne skate off the circuit. He may have clattered a kerb somewhere earlier on the lap.

38 min: This yellow period is bad news for the Ferrari drivers, who left their long run on hard tyres until this late stage of the session.

39 min: Vergne's car remains stranded. Interestingly, his team-mate Ricciardo has just posted a personal best through the first sector...

40 min: Another fastest sector through the problem area on the following lap by Ricciardo, as his team-mate's car is cleared.

41 min: Massa and Alonso, down in 18th and 19th are also posting personal bests in the first sector but must be careful not to speed through yellows

42 min: Vergne confirmed on the radio that he broke the suspension against one of the kerbs in the first sector.

43 min: Massa is discussing the lengthy yellow flags with his team and is told to carry on with his late run, with no time to delay any further.

43 min: Di Resta reports over the radio that whenever he tries to push he is losing rear grip.

44 min: Alonso pops through the pitlane then cruises through the yellow flag zone as Ferrari pays for its leisurely start to the hour.

45 min: Minimal action on track, but the yellows are finally clear and the circuit is ready for fast times once again.

45 min: Alonso, down in 19th after no flat-out laps on hard tyres, is garaged ahead of the medium compound run.

46 min: Vergne is back in the Toro Rosso garage, explaining his view of events to the engineers.

46 min: Raikkonen moves up to seventh fastest as he tries another few laps on the harder tyres.

46 min: Maldonado, di Resta and Hulkenberg join the racetrack.

47 min: Teams are likely eying a longer run than normal on the option tyres, trying to find when the rubber warms up to give good grip.

47 min: Schumacher, Senna and Karthikeyan react to the clear track and come out to play.

48 min: Pic is back out with medium tyres on his Marussia, which is back in working order after that earlier crash with Perez.

48 min: Hamilton leads the field with a time of 1m37.492s with less than 12 minutes of the final practice session remaining.

48 min: Button is out with over 11 minutes remaining to test the medium compound on his McLaren.

49 min: Button is second, just 0.046s down on his team-mate, with Vettel third, Webber fourth, Schumacher fifth and Rosberg in sixth.

49 min: Softer tyres being called for at Ferrari after squandering the opportunity to run early on hards.

51 min: All but the Lotus drivers going for the option rubber now, with that pair holding out for a late qualifying simulation.

51 min: Massa is told that Schumacher found his best time with his fourth effort on the medium compound.

51 min: Vettel, Webber and Rosberg are on the circuit with just under nine minutes to go.

51 min: Massa improves to 15th with his first lap on the options.

53 min: Raikkonen is now on track with the medium tyres on his Lotus but trouble on the other side of the garage as Grosjean's car is jacked up.

53 min: Maldonado is making a move here and looking set to improve, but he gets a wild slide on through Turn 19 and almost comes to grief.

54 min: Little impact from the medium tyres so far as drivers struggle to find pace straight out of the pits.

54 min: Maldonado slid sideways for a good distance in a beautiful four-wheel drift. He eventually ran out of road and had to back out of it.

55 min: Perez moves up to eighth fastest, while Massa finally does find pace in the mediums to go third.

56 min: Ah, Rubinho. Mr. Barrichello makes a welcome visit to a Formula 1 event, along with his friend Tony Kanaan. They are watching on from the Ferrari garage.

57 min: Alonso wobbles wide at Turn 19, spoiling an improved effort. He's currently 13th.

57 min: Vettel lights up the timing screen just as he did yesterday. This is looking good for the German...

57 min: Vettel shoots to the top of the tree with a time of 1m36.490s - more than one second clear of Hamilton.

58 min: Hamilton is quicker than he has been earlier through the final sector but is now over a second off Vettel's new benchmark.

58 min: Maldonado did manage to get a clear lap and he is up to third spot with 1m37.537s in the Williams.

58 min: Massa, deep into a run on the mediums now, clocks a 1m37.871s for eighth fastest.

59 min: Webber is looking for a similar move up the order on this lap. He crosses the line and goes third with 1m37.532s.

59 min: Into the final minute now and the McLaren drivers are still struggling to better their earlier times set on the harder tyres.

60 min: The flag is out on final practice in Texas.

16:00 Maldonado oversteers his way through the end of the lap and goes second with 1m37.001s.

16:00 Alonso finally gets a lap out of his medium rubber for second fastest in 1m37.180s.

16:01 Webber improves with 1m37.298s but the Australian is only sixth in the other Red Bull.

16:01 Massa has also posted a late improvement, but is now shuffled down to sixth.

16:01 Hamilton guns for a final effort, topping the first sector to come around in 1m36.748s and go second to Vettel.

16:01 Vettel came round for another lap but was not able to improve at the end of the session.

16:02 Alonso hacksaws the wheel of his Ferrari through the final corner, failing to improve on his fourth-place time.

16:02 So it is Sebastian Vettel again fastest at the Circuit of the Americas. He tops final practice with 1m36.490s, 0.258s clear of Hamilton.

16:03 Maldonado is a positive third in the Williams, just half-a-second off the ultimate pace and looking good for qualifying. Alonso is fourth.

16:03 Drivers are being allowed to tour around to the grid for practice starts into the uphill first corner.

16:04 Rosberg ends the session in fifth place, ahead of Massa sixth, Webber seventh and this morning's naughty boy Perez in eighth spot.

16:04 Hulkenberg was ninth in the Force India, while Button slipped down the order and rounds out the top 10.

16:05 Other notables: Schumacher was 12th, with Raikkonen a lowly 13th - both finishing 1.27s off the leading pace.

16:05 Vettel makes it a hat-trick of practice sessions at Austin. Can he do the same in qualifying and take pole? Join us later for all the action.

Session length: 60 minutes
Clear skies High Temp: 21°C / 70°F
Track: Dry
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Friday 16 Nov Start GMT
 Friday practice one 14:55
 Friday practice two 18:55
Saturday 17 Nov
 Saturday practice 14:55
 Qualifying 17:50
Sunday 18 Nov
 The United States Grand Prix 18:45