Mark Webber topped the times in opening free practice for Sunday's German Grand Prix, narrowly outpacing Jenson Button.

The 32-year-old Red Bull driver maintained the impressive form shown by his team at last month's British Grand Prix with a fastest lap in one minute and 32.082 seconds.

Button, in his Brawn GP car, was three-tenths of a second slower with Felipe Massa, of Ferrari, third, a further three-tenths adrift of Webber's top time on a cool, damp and overcast morning in the Eiffel mountains.

The conditions were similar to those at Silverstone three weeks ago and once again appeared to favour Webber and Red Bull as Brawn battled to bring the best out of their car.

But while the Australian shone again, it was a difficult morning for Sebastian Vettel, his German team-mate, who came to a halt at the first corner after ten laps. His car needed repairs and he rejoined later on only to wind up eighth-fastest as he struggled to find the form that brought him victory at Silverstone.

Half of the session was lost to the wet conditions caused by early drizzle before Webber took command and began setting the benchmark times for the rest to chase.

Toyota's Jarno Trulli wound up fourth ahead of compatriot Giancarlo Fisichella, of Force India. However, Adrian Sutil, Fisichella's German team-mate, was forced to stop early in the session and had to return to the pits and sit out the practice.

Rubens Barrichello, Button's Brawn GP team-mate, endured a troubled morning and ended up 12th.

Ferrari's Kimi Raikkonen ended the sesson in sixth, Fernando Alonso, of Renault, was 10th, and Lewis Hamilton was 13th for McLaren Mercedes while Heikki Kovalainen struggled to take 18th place.