Kimi Raikkonen's hopes of winning the French Grand Prix receded significantly on Friday after the McLaren title contender suffered a blown engine in practice.
The Finn, second in the Formula One championship to Renault's Fernando Alonso, pulled over after just four minutes of the afternoon session as smoke billowed out from his Mercedes engine, which will now have to be replaced.
"That is obviously going to affect my weekend quite a bit as I will have to move 10 places down the starting grid which will make things more challenging," said Raikkonen.
Under new rules introduced this season engines must last for two successive races. Any replacement within that period brings a 10-place penalty on the grid.
Mercedes said they would fly the engine back to their factory for immediate investigation.
Spanish test driver Pedro de la Rosa, who will not race on Sunday, showed McLaren's pace with the fastest times in both sessions while Raikkonen's Colombian team mate Juan Pablo Montoya was second in the afternoon.
Ferrari's Michael Schumacher, hoping to become the first driver to win the same grand prix eight times on Sunday after three wins in four years at Magny-Cours, was third fastest after being only 11th in the morning.
"I am quite happy with what we have achieved," said the champion. "I think we can be fighting for the win this weekend.
"The team has worked very hard over the past weeks and even months and it seems that all this work is beginning to pay off now," he added.
Alonso, winner of four races this season and runner-up in Magny-Cours last year, has won four of the nine grands prix. Raikkonen has three victories under his belt.
The Spaniard leads the standings with 59 points to Raikkonen's 37.
BATTLE LOOMS
Friday's practice, with De la Rosa lapping well inside the race lap record, set the scene for a battle between Renault, McLaren and Ferrari.
Alonso, who took no points from the previous two North American races, was second quickest in the morning at a home track for both Renault and tyre partners Michelin and will benefit from Raikkonen's misfortune.
"Overall, I think we look quite strong at the moment," said the Spaniard.
De la Rosa's morning time was 1:14.778, with his afternoon best 1:14.460 on a changeable day. Alonso's best was 1:15.183.
Friday's practice marked a welcome return to normality after two weeks dominated by the fallout from the U.S. Grand Prix at Indianapolis, where neither Alonso nor Raikkonen raced after the seven Michelin-equipped teams withdrew.
Schumacher won at Indianapolis, Ferrari's first triumph of the season, in a race of just six cars after Michelin said they could not guarantee the safety of their tyres.
Sunday's race will be the first French Grand Prix in 40 years without a French driver but Olivier Panis provided a local flavour by driving the third Toyota in the practice session.
Panis, the last Frenchman to race in Formula One before he retired last season, was seventh and sixth quickest in sessions.