Beaten in four of the last five races, Formula One leader Sebastian Vettel will aim to reassert his authority at the Belgian Grand Prix.

The defending F1 champion still holds a comfortable overall lead, but his confidence could be shaken if he fails to win this weekend after losing to McLaren drivers Lewis Hamilton and Jenson Button in the past two races. McLaren's tough start to the season has assisted Vettel, the Red Bull driver winning five of the six opening races. The German is not yet out of reach with eight races remaining, however, after his recent dip in form.

"I think we go into the race weekend in a pretty good place. We've won the last two grands prix and the car feels strong," said Hamilton, the 2008 world champion. "We've worked hard to improve the set-up, so it's really inspiring confidence at the moment, which means you can push it that little bit further, particularly in qualifying."

Hamilton won at Spa last year, ahead of Red Bull's Mark Webber, with Vettel in 15th place. After that race, Hamilton led overall with Vettel third, only for the German to make up ground as the championship went down to the final race.

This time, the roles are reversed, with Hamilton in third spot behind Webber and needing to catch Vettel. The problem for Hamilton is that he is 88 points adrift of Vettel, and Button is 100 points back in fifth.

Two-time former champion Fernando Alonso has hit form of late after a poor start by Ferrari to shoot up to fourth, but the Spaniard trails Vettel by 89 points. Webber, who is 85 points behind Vettel, is the only driver in the top five not to have won a race this season.

However, after Red Bull won six of the first eight races courtesy of Vettel, McLaren made significant gains in qualifying and race pace.

"Despite winning three of the last five grands prix, we are still hugely determined to be stronger than before," McLaren team principal Martin Whitmarsh said. "Time and time again, McLaren Mercedes has proved its resilience and determination, particularly at this crucial stage of the world championship. We are more than ready for this fight."

Button and Hamilton have two race wins each so far this season, but McLaren still lags behind Red Bull in qualifying.

Red Bull has taken all 11 pole positions so far, with eight for Vettel and three for Webber. Starting from pole is crucial for Vettel because only one of his 16 career wins has come when starting behind the front row.

Yet the momentum is clearly with McLaren. Button, the 2009 champion, is brimming with confidence after his brilliant victory at last month's Hungarian GP.

"Our aim will be to put pressure on the championship front-runners ... our car definitely feels really drivable right now," Button said. "It felt great to go into the summer break off the back of the win in Hungary."