Jenson Button admits that Sebastian Vettel is now best placed to retain his F1 title this season, but insists that McLaren hasn't given up hope of overhauling Red Bull in the constructors' championship.

Vettel closed to within four points of Ferrari's Fernando Alonso with his victory in Japan last week and will start this weekend's Korean Grand Prix as one of the favourites given Red Bull's performances at the Yeongam circuit in the past.

Button remains in contention for the title himself but is 63 points down on Alonso and he admitted that it is Vettel - who heads into the Korean race just four points behind - who is the now the championship favourite.

"They've been competitive for many races," he told Sky Sports in reference to Vettel's Red Bull team. "In Suzuka they took another step forward, yes, and they had some new parts on the car. Obviously the double DRS but I don't really know how much that helped them.

"You would say at the moment that Sebastian and Red Bull are in the best position to fight for the Championship. They're very, very strong. But you can never discount Ferrari and Fernando.

"They could bring something here which gives them a couple of tenths, or three or four tenths, and then they are back at the front again."

McLaren's most realistic chance of silverware this season will come in the constructors' championship with a gap of 41 points to Red Bull - with Button confident that they could be caught.

"We could claw that back in one race in one race, that's the great thing - if we both get a good result and those two don't," he said. "The constructors' is definitely on. When I get out of the car at the end of the race and I look at the points, that's the bit I really look at.

"The drivers' is such a slim opportunity. If it happens, it happens. But I'm not going to get too excited about it."