Montoya is one of Formula One's most exciting talents

McLaren boss Ron Dennis said: "The opportunity to sign a talent like Juan Pablo was too good to miss."

The move is likely to spell the end of David Coulthard's McLaren career - Montoya is expected to partner Finn Kimi Raikkonen.

Dennis added: "There is already a considerable amount of anticipation within our team about 2005."

A statement from McLaren said the team would announce its full 2005 line-up at a later date, although Raikkonen is considered all but certain to stay on.

Coulthard's manager Martin Brundle told this website the Scot was simply concentrating on next season.

"It's not great news for David, but 2005 is a long way off and many things can happen in that time," said Brundle.

CAREER DETAILS - MONTOYA 1998: Formula 3000 champion 1999: Cart champion 2000: Indianapolis 500 winner 2001: Moves to F1, takes first win in Italy 2002: Third in championship, seven pole positions 2003: Third overall, two wins Profile: Juan Pablo Montoya

"We have a contractual position moving forward with McLaren and David is just focusing on 2004."

A partnership of Raikkonen and Montoya would give McLaren arguably the most exciting driver line-up in F1 as they attempt to end Ferrari's domination of the sport.

McLaren's attempt to sign Montoya was revealed by the BBC Sport website in July.

The team initially wanted to take him for 2004, for which he was already contracted to Williams, but had to give up that idea when Williams insisted he stay on.

Montoya, who finished third in the world championship behind Michael Schumacher and Raikkonen this year, said: "This is a great opportunity for me and I'm really looking forward to the first time I will be able to drive one of McLaren's cars.

"To join them is an amazing challenge and experience which I plan to fully enjoy.

"However, my short-term aim is to concentrate 100% on winning the 2004 world championship."

Montoya's move to McLaren comes as no surprise to anyone From Kris Ward Have your say

Montoya will attempt to do that at BMW Williams, in what could be a difficult year for the team.

His departure to McLaren puts Williams and their engine partner BMW in a difficult position.

That is because Montoya will be able to tell his new employer, whose engine partner is BMW's bitter rival Mercedes-Benz, many of Williams' latest secrets.