TOTO WOLFF insists his Mercedes team could still miss out on Formula One glory this season despite leading both championships.

Lewis Hamilton heads team-mate Nico Rosberg in the drivers' championship by 21 points with Ferrari's Sebastian Vettel, a winner at the Hungarian Grand Prix in July, 42 points adrift of the Briton.

Mercedes, who have won eight of the opening 10 races this season, are also 147 points clear of Ferrari in the race for the constructors' title ahead of this weekend's Belgian Grand Prix.

But Wolff, mindful of Hamilton and Rosberg finishing sixth and eighth last time out in Hungary, and their first-lap collision at Spa-Francorchamps 12 months ago, insists neither title race is a foregone conclusion.

"With 10 races down and nine to go, we enter the second half of the season with a stronger points total than at this stage last year, and yet our margin to the competition is actually smaller," said Wolff ahead of this week's Belgian Grand Prix. "There is never a moment you can take your foot off the gas and Hungary proved once again that any slip is an opportunity our rivals will grab with both hands."

The Mercedes motorsport team principal added: "We have all enjoyed a chance to recharge over the summer – but we have also kept our minds focused on what lies ahead. There are still many chances to win or lose this battle and we must be relentless in our push to come out on top."

Hamilton has revealed he is itching to get back into his Mercedes cockpit with the F1 calender set to emerge from summer hibernation.

The world champion, who finished sixth at last month's Hungarian Grand Prix following an error-strewn performance, has holidayed in Barbados and New York.

But Hamilton now has his sights fixed on winning in Belgium and strengthening his position in the race for this year's championship.

"It's been good to take a break from racing and spend some time relaxing, training and recharging the batteries," said Hamilton, who last won at Spa in 2010. "There's always that flame in the back of your mind that just wants to get back out there and get on it – especially after a race like Hungary.

"Spa is a great track to kick off the second part of the season too. It's one of the really great, old-school circuits with so much history. It's mostly medium to high speed corners, so you're pretty much pedal to the metal the whole way round which is a lot of fun.

"It's always special to come out on top at a classic race like this so I remember winning here well. I love this track and I'll be gunning for that top spot again."

Despite his erratic display at the Hungaroring, Hamilton was somehow able to extend his lead over Rosberg in the championship to 21 points.

The German was battling for the victory with his compatriot Sebastian Vettel before he collided with Red Bull's Daniel Ricciardo in the closing stages. He crossed the line in eighth.

"Hungary was a big disappointment and I've been itching to get back to racing ever since," Rosberg, who was reportedly hit with a six-figure fine following his crash with Hamilton at Spa last season, said.

"When you're in such a close battle for the championship, any opportunity to gain points is crucial and it's up to me to take those chances – but also to make them for myself. That's definitely the target for the second half of the year.

"We're only halfway through the season, so it's all still to play for. Spa is a fantastic circuit – a track that I think every driver enjoys and one that always produces spectacular racing. I'm looking forward to it."