Montoya has one year left to run in his contract with the WilliamsF1 team, after having finished third in this years Drivers championship.

Montoya commented on his move by saying: "I am thrilled to be joining West McLaren Mercedes. The team is consistently a strong World Championship contender and has a fantastic heritage. It's a great opportunity for me and I'm really looking forward to the first time I will be able to drive one of their 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 percent on winning the 2004 World Championship."

McLaren head Ron Dennis said: "We want to win races and World Championships, and in order to do so we have to plan for the future whilst applying every effort in the short term. The opportunity to sign a talent like Juan Pablo was too good to miss, and there is already a considerable amount of anticipation within our team about 2005.

"Juan Pablo has achieved a considerable amount of success in his career and we are certain that he will add to this with West McLaren Mercedes. We are certainly looking forward to seeing what he can do in one of our cars and I believe that it's a prospect that can't fail to excite Formula One fans around the world. However until that happens we will be focusing all efforts on our 2004 Championship challenge."

As for the early announcement regarding Juan Pablo's move a a McLaren spokesperson said: "It's in everyone's interest to confirm Montoya's contractual position with the team and end any speculation regarding our 2004 line up."

The WilliamsF1 team has not made any comment on the announcement by McLaren. Speaking for the WilliamsF1 team Media Manager Liam Clogger said: "Frank Williams maintains that all the facts are laid in McLaren's statement and we have nothing to add to it."