Sebastian Vettel heads Mark Webber in US GP second practice

By Andrew BensonChief F1 writer in Austin, Texas
Sebastian Vettel on top in Texas

Sebastian Vettel led Mark Webber to a Red Bull one-two in second practice at the United States Grand Prix.

The German, crowned world champion two races ago, beat Webber by 0.115 seconds, with Mercedes' Nico Rosberg third from team-mate Lewis Hamilton.

Lotus's Heikki Kovalainen was fifth, from the Saubers of Esteban Gutierrez and Nico Hulkenberg and team-mate Romain Grosjean.

McLaren's Jenson Button was ninth ahead of Ferrari's Fernando Alonso.

Alonso fastest in fog-hit first practice

Button has been given a three-place grid penalty for ignoring red flags in the first session on Friday morning in Austin.

Apparently struggling with his car, Hamilton made a series of mistakes in the early part of the session and ended up 0.173secs behind Rosberg.

He told his team he wanted to do another low-fuel qualifying simulation lap, but the team refused, telling him he had to get on with his high-fuel race-preparation run.

Hamilton said he had had "an OK day", adding: "The Red Bulls are a long way down the road but we'll still try to give them hell and catch them."

Vettel was fastest despite being blocked by Grosjean on his first attempt at a flying lap, and by a Williams on his second, so his tyres were not at their best when he set his fastest time.

The Red Bulls were also in a league of their own on the race-simulation runs in the final part of the session - Vettel was nearly a second a lap faster than the best driver from any other team, with Webber a few tenths of a second behind his team-mate.

BBC F1 technical analyst Gary Anderson said: "I think Vettel and Webber will be the front row but I think Mercedes will be keeping them honest. If a Red Bull makes a mistake a Mercedes could sneak onto the front row."

Arguably the most impressive performance of the session came from Kovalainen.

Drafted in by Lotus as a replacement for Kimi Raikkonen, who is missing the last two races of the season to have an operation on a long-standing back problem, he was competitive on both low and high fuel.

He was about 0.2secs quicker than team-mate Romain Grosjean on single-lap pace, although the Finn appeared to be lagging behind the Frenchman on race pace.

Lotus technical director Nick Chester said Kovalainen had done "a brilliant job".

Re-born in the USA - F1 in America

With Red Bull already winners in both the drivers' and constructors' championships, Ferrari face a battle to get back the second place in the constructors' championship they lost to Mercedes a couple of races ago and just as much of a struggle to hold off Lotus, who are catching them in fourth place.

Ferrari also appeared to be lagging behind Sauber, in both low-fuel and high-fuel trim. The Italian team appear to have a difficult weekend ahead.

See a full list of second practice results.