Ferrari's Fernando Alonso insists his chances of winning the Formula One championship aren't over yet, despite Red Bull's Sebastian Vettel winning the past four races and driving a faster car.

Their duel resumes this weekend at the Abu Dhabi Grand Prix.

Trailing Vettel by 13 points with three races remaining, Alonso knows his car's pace has to improve for him to have any chance of catching the two-time defending champion. The Spaniard finished a distant second to Vettel at the Indian GP last weekend. He had finished no better than third in the previous five races, and the commanding lead he held in the standings over the summer has quickly evaporated.

Kimi Raikkonen of Lotus is 67 points back in the standings in third, while Vettel's teammate Mark Webber is another six points behind.

"We believe and trust in our job and our team," said Alonso, who last week guaranteed Ferrari would still win the championship.

"We showed many times that we don't give up and we will fight until the end," he said. "When things become stressful, when things become difficult, we can deliver 100 percent. The team has a lot of experience fighting for a world championship and everyone is very motivated."

Ferrari is actively trying to improve Alonso's car, and new parts are due in by Friday. Alonso said he doesn't expect those changes to close the gap immediately, but he said a more competitive car could put pressure on Red Bull and take advantage of any mistakes Vettel makes.

"They had an easy four races, had a lot of margin and they can do little mistakes with no penalty," Alonso said. "We want to be so close to them to take the opportunity of everything they don't do perfect. We need to find perfection this weekend or these next three weekends."

Vettel is on the verge of clinching a third consecutive driver's championship. He can't do it this weekend, but a win would almost certainly allow him to clinch the title later this month with a strong performance at the U.S. Grand Prix in Austin, Texas.

If so, he would join Juan Manuel Fangio and Michael Schumacher as the only drivers to win three championships in a row.

"It depends on how it comes to an end. That is why we are here," Vettel said. "There are three races to go. It's no secret everyone is important. You don't get more points than five races or 10 races ago. We try therefore to have the same approach we had 10 races ago."

Vettel, who clinched the 2010 title in Abu Dhabi and then ran away with the title in 2011, has had a late resurgence after struggling with his car early in the season. He has won the past four races but knows that success can be fleeting.

After earning the pole at last year's Abu Dhabi Grand Prix, he crashed on the opening lap due to a punctured tire. He also has retired twice this season with alternator failures.

"If you just look back at India, it was a great race for us but a couple laps before end we had some sparks," he said. "It doesn't take much to imagine. If something like this comes up, it shows you how vulnerable you are no matter which position you are — in the lead by a big gap or just in middle of the field fighting for position."

Red Bull can clinch its third consecutive constructors' championship this weekend. It leads Ferrari by 91 points and McLaren by 101. That means Ferrari must score six points more than Red Bull to keep that race alive while McLaren need to score 15 points more.

"It would be a great success for us," Vettel said. "I didn't know until Mark told on the way back from India. We just spoke very shortly about the constructors. We were both on the same plane and Mark said it would be quite bad for constructors if this plane went down."

McLaren's Lewis Hamilton has shifted his attention to the constructors' championship now that he and teammate Jenson Button are out of the title chase. Since announcing in September he would replace Michael Schumacher at Mercedes next year, Hamilton has not had a podium finish. But he said he remained committed to helping McLaren win the title.

"I've just been focused on trying to get this constructors' championship for the team and try and get the maximum we can," he said. "In theory it's still possible for us to win and so all guns blazing for that."