Williams co-owner Patrick Head has admitted the uncertainty over Renault's future in Formula 1 has delayed plans to confirm its engine supplier for the 2010 season.

Williams were thought to be on the verge of reigniting its relationship with the French manufacturer next year through a supply of customer engines, replacing its current agreement with Toyota.

However, the announcement has been put off following allegations that Renault was involved in fixing the result of the 2008 Singapore Grand Prix, when it asked Nelson Piquet Jr to crash in order to help team-mate Fernando Alonso to win the race.

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With the manufacturer due to appear before the World Motor Sport Council on Monday, Head is concerned that a potential ban, or a subsequent withdrawal from the manufacturer itself, will cause problems in its preparations for 2010.

"It certainly doesn't make it any easier," he said. "We're not yet concluded on which engine we'll be running next year, but we hope it won't be too much longer."

Head went on to admit he had approached Mercedes-Benz about a possible supply too. However, with the German manufacturer already supplying McLaren, Brawn GP and Force India this year, it is rumoured to be taking on just one other team - Red Bull - next year.

"I think it's fairly well known up and down the pit lane that Mercedes, within the limits of what they are allowed to develop within the homologation, seem to have made more progress than the other teams at improving their engine and it's now clearly a very good engine," added Head, who also said a return to Cosworth was an option.

"We certainly showed some interest a couple of months ago but we were informed that it was not available to us."

Williams and Renault forged a hugely successful partnership during the 1990s, winning five of its nine manufacturer titles together.