Italian Jarno Trulli is expected to join Ralf Schumacher at Toyota after announcing on Sunday that he will leave Renault at the end of the Formula One season.
"I am happy with this decision and feel very confident as my plans for the future are clear," he said in a statement at the German Grand Prix.
The 30-year-old did not say where he would be going and although Williams have two vacancies, a move to big-budget Toyota has been taken for granted in the paddock for some time.
Ralf Schumacher, who has already signed for the team, told reporters on Saturday that Trulli would be his first choice as team mate.
"If that was possible, that would obviously be my first choice and that would really suit me," said the German, recovering from injuries sustained in last month's US Grand Prix.
Italian Trulli won this year's Monaco Grand Prix, his first victory since he came into Formula One with Minardi in 1997, and is the only driver other than Ferrari's world champion Michael Schumacher to have triumphed this year.
A move to Cologne-based Toyota would reunite the Italian with former Renault technical director Mike Gascoyne, who rates him highly.
"I've always said over one lap I think he's one of the quickest guys out there," Gascoyne said at Hockenheim. "He's been consistent and really he's been carrying Renault. He's why they are second in the championship at the end of the day.
"You want quick people," he added. "We are very well aware we need someone who will get on with Ralf and not wind him up."
Trulli has had an eventful season, winning at Monaco and then incurring the wrath of his team when he ceded third place within sight of the finish in France.
Trulli's move ended his three-year stint at Renault, the longest he has stayed with any team. He drove for Prost in 1998 and 1999 and Jordan in 2000 and 2001.
"I remain as motivated as ever and am fully focused on thecurrent championship," he said on Sunday. "This season has been a very successful one and I intend to add more achievements, for myself and the team, before it is over."