SPA-FRANCORCHAMPS, Belgium — McLaren's Lewis Hamilton was fastest in practice Friday for the Belgian Grand Prix, where Red Bull looked poised to cut into Brawn GP's Formula One championship lead.

Defending F1 champion Hamilton lapped the 4.352-mile Spa-Francochamps circuit — the longest on the calendar — in 1 minute, 47.201 seconds during the afternoon session.

"I'm definitely not unhappy but I know it can be better," Hamilton said. "I don't think we're fastest. But it's looking much better than we anticipated."

Hamilton, coming off a victory at Hungary and a second-place finish at the European GP, was one of two drivers not to be classified during a rainy morning practice.

Toyota's Timo Glock was second ahead of Kimi Raikkonen of Ferrari, with both drivers a fraction of a second off Hamilton's pace.

Red Bull's Mark Webber was fourth — 0.128 seconds behind Hamilton — while teammate Sebastian Vettel was 10th after having skipped the morning session to save his engine. He has only two — including his current one — for the final six races.

"We've been nursing the engines a long time now," said Webber, who has three spare engines. "Both of us got through them today without any problems."

Vettel is trying to make up a 25-point gap on Brawn GP's Jenson Button, who leads the overall standings with 72 points.

Teammate Rubens Barrichello — coming off his first victory for five years at Valencia, Spain — is second in the standings with 54 points followed by Webber on 51.5.

"We cannot get beaten by Brawn here. We have to beat them, both of us do," Webber said. "We can't lose points to them here."

As expected, the Brawn GPs struggled on a track characterized by long straights, high speed corners and cool weather. Button was 17th and Barrichello 18th, both nearly one-second off the pace.

Red Bull is also trying to trim a 27.5 point constructors' series deficit to Brawn GP.

Luca Badoer's role as Felipe Massa's replacement at Ferrari could be threatened after the 38-year-old Italian driver finished last of the 20 drivers — 2 seconds off of Hamilton's pace and nearly as much off of Raikkonen, a three-time winner here.

"It's simply a question of finding my rhythm," Badoer said. "Every run I am improving."