Williams: BMW Alliance is Long Term

However, the team did not categorically deny reports that they had been in negotiation with Cosworth and Toyota over a future engine supply.

"It is well known that Williams never comments on contractual matters," said team boss Frank Williams in a statement. "We have a long-term alliance with BMW and we are very, very happy with it. Any close partnership like this will have the occasional issue, but fundamentally we have an excellent team."

Williams have a contract with BMW until 2009, but the Munich manufacturer looks likely to supply Swiss-based Sauber as well next season.

There have been reports in Germany suggesting also that the carmaker is losing patience with Williams, winners of nine Constructors' and seven Drivers' Championships but without a title since 1997. Some have suggested BMW could even buy Swiss-based Sauber and join Ferrari, Renault and Toyota as manufacturer-owned teams doing everything in-house.

Since they joined forces in 2000, Williams and BMW have won just 10 races. Champions Ferrari, dominant throughout that period, won 15 last year alone.

Asked whether the possibility of BMW supplying a second team had encouraged Williams to consider other engine partners, Williams replied:

"Several weeks ago, five of the manufacturers announced they would supply independent teams with an engine - i.e. every manufacturer would provide a second team with an engine. We strongly support this initiative because it underpins the future of Formula One."

The carmakers, with the exception of Ferrari who have already sided with Formula One supremo Bernie Ecclestone in agreeing to extend an existing commercial agreement to 2012, are planning their own series from 2008.

To encourage the so-called independent teams to join them, they have promised affordable engines from 2006 if other conditions are met.

Williams, who said last month that he saw no threat to Williams in BMW doing a deal with Sauber, denied that the media speculation had been damaging to his team.

"There are plenty of reasons why these rumours are perpetuated," he said. "But the facts are quite simple from our perspective. BMW are our choice of engine supplier. We have a long-term alliance with BMW with which we are extremely happy."