Lewis Hamilton has been training hard during Formula One's midseason break. His goal is clear: He wants to catch leader Sebastian Vettel with nine races left.

Hamilton, who won from the front at the Hungarian Grand Prix last month, begins his work at Sunday's Belgian Grand Prix, where he will be looking to secure his fourth consecutive pole position. The Mercedes driver is fourth overall and has 48 points to make up on Vettel, the three-time defending champion.

Hamilton usually spends the midseason break relaxing but this time he chose to increase his training regime and has not given up hope of repeating his 2008 title.

"There's still a long way to go in the championship so nothing's impossible," Hamilton said. "I feel good in myself, coming here knowing I have a car I can fight with.

"I've been training really hard over the break, which has been a lot different to the last six years," he added. "The last six years I've taken it as a real holiday. I just fancied doing something different. I just really kept myself busy. I wasn't on the beach chilling."

At the same stage last season, Hamilton was dealing with issues surrounding his future and tensions between him and Jenson Button escalated in tandem with the speculation.

"Not knowing where I was planning to go was a constant drain, taking away energy," he said. "It's just a great feeling coming here. I'm settled in my new team, happy where I am now, looking forward to a successful three years with them."

Vettel was in a similar position to Hamilton last year, coming to Spa trailing Fernando Alonso by 42 points. He clawed those back and won the title at the last race.

Vettel is 38 points ahead of Kimi Raikkonen and 39 ahead of Alonso. But Hamilton is expected by many to emerge as Vettel's direct challenger.

"Mercedes has been very, very competitive, not just Lewis. Also Nico (Rosberg), who won two races," Vettel said. "We know that they're very quick in qualifying. Hungary, in a way, for the first time they had the ability to show their speed in the race as well."

Hamilton's win in Budapest was indicative of a marked improvement in the car's consistency. While Mercedes had the speed advantage over Red Bull it lacked durability for a whole race.

"Surely the last couple of races they were most competitive," said Vettel, who still considers Alonso and Raikkonen a threat.

"Lotus have always been there scoring points with Kimi. Ferrari has a bit of a lull at the moment, still they've got good points," he said. "All of these teams and these drivers you have to keep them in mind. For us it's not that important to pick one particular driver."

Vettel gets along well with Raikkonen and is disappointed he will not get to drive alongside the Finn next season. The Red Bull seat is up for grabs since Mark Webber announced he will retire from F1 at the end of the campaign.

"First of all, I didn't know how realistic it was or not. It looks like it's not the case," Vettel said. "Kimi would have been nice in many ways ... Who knows? He's young, I'm still young, a lot of things can still happen. But probably not for next year."

The 33-year-old Raikkonen's Lotus future remains unclear. He has been linked with a move to Red Bull and also to Ferrari, but the Red Bull move appears over because Daniel Ricciardo is widely expected to step up from Toro Rosso and replace Webber.

"Ideally, you would like someone who is competitive, as competitive as you are, so that we're pushing each other. You don't have to be best friends with whoever is racing next to you," said Vettel, who has had several high-profile spats with Webber over the years.

"You need to work for the team, I think that's one of the most important bits," Vettel added. "So that you work in the same direction and hopefully ensure that the car gets faster."