Red Bull's Sebastian Vettel will aim for his seventh win of the season from pole position at the Belgian Grand Prix, after holding off Lewis Hamilton's McLaren in difficult weather conditions to win yesterday's action-packed qualifying session.

The defending Formula One champion starts from the front for the ninth time this season, with his Red Bull teammate Mark Webber, celebrating his 35th birthday and a new one-year contract with Red Bull, securing third place.

Vettel has a commanding lead of 85 points over Webber in the overall standings, and leads Hamilton by 88.

Red Bull has now secured pole for every race so far this season, although Webber had looked the more likely to do so before Vettel's late burst.

Vettel had not looked particularly sharp in any of the three rain-affected practice sessions.

"I didn't feel comfortable at the beginning," he said.

But the German produced his best late in qualifying as the track started to dry out.

Vettel, who has not won for the last three GPs, joked that the only way to get a reliable weather prediction at Spa is "to look up to the sky and see what's happening" just before the race starts.

Webber, still looking for his first win this season, was disappointed to miss out on his fourth pole position.

Jenson Button's hopes of following up his win at the Hungarian Grand Prix took a blow as he failed to make the third and final qualifying session, and the British driver will start back in 13th on the grid.

Button was left stunned as he and his team misjudged the situation by coming in too early to cool his tires, missing the chance to do another lap.

"I was second quickest when I did my lap, and then I didn't get another chance," Button said. "That is massively disappointing and a huge shock. A big mistake on our part."

Seven-time former champion Michael Schumacher, racing at Spa 20 years after making his F1 debut on this track, crashed out on the first lap of the first qualifying session and will start the race in last place.

Felipe Massa rescued a poor session for Ferrari by taking fourth place on the grid, but two-time former F1 champion Fernando Alonso starts from eighth spot – although it could have been even worse for the Spaniard.

With the clock ticking down in the second qualifying session, Alonso was lagging in 11th place, but finally managed to get a clear run and then set the best time.

McLaren also had an eventful Q2, with Hamilton colliding with rookie Pastor Maldonado's Williams as he approached the line. The repairs were only minor and did not seem to impede Hamilton in Q3.

Hamilton was unsure what to make of the incident, although it appeared that Maldonado had cut across him.

Massa survived a scare early in Q3 when he took a corner too wide and skidded over the grass.

After heavy morning rain, the track had dried somewhat for the start of the first qualifying session, although dark clouds stretched across the 7-kilometre circuit.

Vettel closed his eyes for a few seconds as he prepared to start.

Barely a minute into qualifying, Schumacher's Mercedes slid across the track backward and hit the crash barriers, sending the car's back rear wheel tumbling down the track.