Williams has requested a release from its engine contract with Toyota for 2010, AUTOSPORT has learned, with the team now weighing up its options about which power-unit to run next year.
Although Williams has another year to run in its partnership with the Japanese manufacturer, moves are now being made for the deal to finish at the end of this year.
It is understood that Williams has already held talks with several car manufacturers about a supply for 2010 - with Renault emerging as favourites for a new partnership, although Mercedes-Benz could also be a possibility.
Team boss Frank Williams told AUTOSPORT that he expected a decision about the identity of the engine partner to be made imminently.
"It will be quite soon," he said. "We have got to find a way to put it into a car, haven't we?"
Although AUTOSPORT understands that talks have already opened with Renault about a potential supply deal for next year, Williams declined to comment on who was favourite if the team's deal with Toyota comes to an end.
"The paddock is full of gossip," he said when asked if Renault was his preferred option. "Tomorrow it might be Mercedes-Benz, and then the next day Ferrari - and I get a free car with it!"
Toyota has confirmed that it is 'flexible' to the possibility of Williams ending its deal early - providing it was not hurt financially by the move.
"It is a slightly complex situation," team president John Howett told AUTOSPORT. "The original document we gave the right for Williams to seek an alternative engine. The basis was that should they get a free engine in the future, perhaps from a new entrant manufacturer, then we would not be there to damage Williams in any way with purely contractual relations.
"Earlier this year they pushed us to sign an extension agreement covering specifically next year, which we have concluded, but they are asking, or seeking, to find an alternative supplier.
"Toyota's position is normally flexible. If they do not wish to take our engine, I don't really feel materially, provided we can reduce the stock and are not left with any liability, that we hold them to the contract."
Renault has been pushing hard to keep its customer supply operation in place for next year, and AUTOSPORT understands it has upped its efforts to try to convince current partner Red Bull Racing to extend its successful partnership.
Red Bull Racing is seriously considering a switch to Mercedes-Benz for next year, but a hard push from Renault chiefs to show its commitment to helping the Milton Keynes-based outfit appears to have put the French car manufacturer back in the frame again.
Christian Horner, team principal of Red Bull Racing, said his outfit would take its time before deciding what it would do.
"We have still got time on our hands," Horner told AUTOSPORT. "Renault is doing a great job for us, showing great support, but we are not in any rush."