Button confirms Williams drive

In the last few hours, BAR has even issued an ultimatum to Button's management company Essentially Sport, requiring him to attend a face-to-face meeting with BAR's management, by close of business Monday, or face immediate action to enforce BAR's contract with him. But despite all this, Button's mind seems set on a return to the team that introduced him to F1 nearly four years ago.

"I'm going to be driving for BMW Williams," he said. "I can't give any information away. I'm not a legal expert, but based on the information I have I am able to drive a BMW Williams car next year.

"Formula 1 is not just about this season. I need to look into the future and to me the resources at BMW and Williams are fantastic and they are a team that will be challenging for the world championship next year. That is really what I want and what I need."

Button has admitted that he expects the jovial atmosphere in the BAR pit to disappear but says he had to put his ambition to become a world champion before all other considerations: "It's difficult you know, things do change in F1. For me, my main aim is to be world champion and I want to challenge Michael Schumacher for the world championship in the next few years. To do that I think Williams is the best team.

"The resources at BMW and Williams are far greater than most teams on the grid. It's the team that brought me into F1 and I know how they work. Also having Mark [Webber] as team-mate there will make us a very strong team."

Button says he believes he has fulfilled his role with BAR and says he wants to move to a place where he reckons will give him a genuine crack at the world title, even despite the fact that his current team is nearly 30 points ahead of Williams in the Contructors' Championship standings.

"My commitment was there [BAR] for the last two years," he said. "That was my contract and I have fulfilled that. They have been a great team. A really good team to work with and I have enjoyed every moment with them, good and bad. It's been very exciting and obviously for the rest of the year I am still going to fulfil my contract.

"The atmosphere is going to be a bit different from the start of the season obviously, but these things do happen. This is an opening that we can use to move to BMW Williams, and I think that team will be the team to be with in the future. Obviously as I said, BAR have done a great job and I've enjoyed working with them."