Lewis Hamilton will leave McLaren at the end of the Formula One season and join Mercedes, reports said on Friday.
The 27-year-old Briton's move will be formally announced later in the day, the BBC and the Press Association news agency said.
The three-year deal will be worth £15 million ($24 million, 19 euros) to the 2008 world champion, PA said.
He will be replaced by Sauber's Sergio Perez at British-based McLaren, reports said.
Speculation has surrounded Hamilton's future after he was initially offered a pay cut of a third on his £10 million-per-year deal by McLaren, putting him on a par with team-mate Jenson Button.
Reports said they later increased that by a further £2 million.
The 27-year-old Briton is fourth in the overall standings, 52 points behind leader Spaniard Fernando Alonso heading into the last six races after suffering a gearbox failure during the Singapore Grand Prix.
Hamilton has won three races this season, in Canada, Hungary and Italy, and finished on the podium in the opening three races in Australia, Malaysia and China.