Lewis Hamilton is on the verge of leaving McLaren to drive for Mercedes next season, according to BBC F1 chief analyst Eddie Jordan.
The former team boss says Hamilton will replace Michael Schumacher, who will retire from driving for a second time at the end of the year.
"I believe Hamilton and Mercedes have already agreed personal terms and a deal could be imminent," Jordan said.
In a statement Mercedes said they "do not comment on speculation".
But they added: "Until we are in a position to confirm our full driver line-up for next season, it is inevitable that there will be speculation around this topic."
A McLaren spokesman said: "We have been told by Lewis Hamilton's management team that the story is untrue.
"Negotiations between Lewis Hamilton and McLaren [over a new contract] continue."
It would appear Michael [Schumacher] is leaving and Lewis is arriving at Mercedes
Hamilton's management team XIX Entertainment also released a statement, saying: "As mentioned in the past by all parties, we are in advanced discussions with McLaren about a new deal.
"More importantly, at the moment, Lewis is focused on Monza [this weekend's Italian Grand Prix] and competing strongly for the championship."
However Hamilton's management have also approached Red Bull and Ferrari this summer but been rebuffed.
F1 boss Bernie Ecclestone hinted last Sunday that Schumacher was retiring.
Ecclestone told Jordan on BBC One: "I'm sorry that he's leaving us not being a winner, because he is a winner."
Asked if he knew whether Schumacher was retiring, Ecclestone added: "I don't know, I don't know."
Confronted with Ecclestone's comments, Schumacher insisted after Sunday's Belgian Grand Prix that he had not yet decided on his future.
"As I told [Ecclestone] yesterday I had not made a decision," said the German.
Jordan said he had since been investigating the situation and believed Hamilton, who has yet to agree a new deal to remain with McLaren, was on his way to Mercedes to replace Schumacher.
"Some weeks ago I said on TV that I felt Lewis was on the move and I had an idea at the time he had been speaking to Ferrari, which we now know is true," Jordan said.
"But I can now confirm his people have had meetings with Mercedes.
"Bernie Ecclestone made it clear to me live on television on Sunday that Schumacher was leaving, although Schumacher later played it down.
"So it would appear Michael is leaving and Lewis is arriving at Mercedes.
"Hamilton has not agreed terms with McLaren yet.
"In fact the team have made it clear they cannot offer him as big a salary as his current $15m (£9.42m) deal, which was negotiated before the global financial crisis.
"On top of that, McLaren have to pay for their Mercedes engines for the first time next year.
"Hamilton moving to Mercedes would also make a lot of sense in the context of his manager Simon Fuller, the man behind the Spice Girls and now David Beckham.
"Fuller is trying to position Hamilton as a major global star, like Beckham, and Mercedes is a much bigger global brand than McLaren.
"There has been some uncertainty over Mercedes' position in F1. The board is unhappy at the current performance of the team, but getting Hamilton would undoubtedly be a massive coup and it could give the F1 team some breathing space."
If Hamilton left McLaren, it would leave the team with a huge hole to fill.
Among the candidates for the vacancy alongside Jenson Button would be Scot Paul di Resta, currently at Force India, and Lotus driver Kimi Raikkonen.
Di Resta, who has the same management team as Button after splitting with Hamilton's father Anthony, has continued to impress this season, his second in F1 with Force India.
Raikkonen, who drove for McLaren from 2002-06, was a candidate at the team for 2010 before negotiations broke down over money and team boss Martin Whitmarsh turned to Button.
Raikkonen returned to F1 this season with Lotus after two unsuccessful years in world rallying and although he has had some unconvincing weekends, his performances have been increasingly impressive.
BBC Sport understands Raikkonen is on course to satisfy performance clauses in his contract that would commit him to Lotus in 2013, which would mean any team that wanted him would have to pay Lotus compensation.
The 32-year-old Finn currently lies fourth in the championship heading into this weekend's Italian Grand Prix, one place ahead of Hamilton.
The Englishman's season has been hampered by early-season operational errors by McLaren which cost him about 40 points, and on Sunday in Belgium he was taken out in a start-line collision caused by Lotus's Romain Grosjean.
Hamilton is now 47 points behind world championship leader Fernando Alonso of Ferrari with 200 available in the remaining eight races. BBC Sport - Lewis Hamilton 'set for move to Mercedes from McLaren'