By Alan Baldwin
YEONGAM, South Korea (Reuters) - Lewis Hamilton kept Sebastian Vettel off the top of the timesheets on Friday in a first practice session for the Korean Formula One Grand Prix that saw Kimi Raikkonen crash his Lotus into a wall.
The Mercedes driver lapped the anti-clockwise Yeongam circuit, set against a backdrop of coastal marshes and sprawling South Korean shipyards, with a best time of one minute 39.630 seconds.
Red Bull's runaway championship leader Vettel, chasing his fourth win in a row since the end of August and third in succession in Korea, was second quickest a mere 0.037 slower after firing in his best lap in the closing seconds.
Raikkonen, who struggled with a bad back in Singapore two weeks ago, skidded hard into the tyre wall at the final corner in the closing seconds but clambered out of the car without any apparent difficulty.
The 2007 world champion's time was the eighth best on a sunny and cloudless day.
Red Bull's Mark Webber, who will have a 10 place grid penalty on Sunday after collecting his third reprimand of the season for a Singapore post-race 'taxi ride' on Fernando Alonso's Ferrari, was third fastest.
Hamilton's team mate Nico Rosberg reinforced the idea that the battle lines were drawn between Mercedes and Red Bull with the fourth best time ahead of McLaren's Jenson Button and Alonso.
Vettel is 60 points clear of Alonso with six races remaining, meaning a fourth successive title is almost within reach, and was in a league of his own on the streets of Singapore.
The 26-year-old German is again the favourite although Mercedes could make life harder for him.
Marussia's Venezuelan test driver Rodolfo Gonzalez also hit the wall early in the session when he was almost alone on the circuit.
Britain's James Calado was also given time in the Force India, with compatriot and race regular Paul Di Resta sitting out the session.