MONACO May 25 Mercedes are talking to Williams about a Formula One engine supply from 2014, the German company's motorsport head Toto Wolff said on Saturday.
Mercedes are already contracted to supply their own works outfit, Force India and McLaren next year but the latter team have announced they will be reviving their partnership with Honda in 2015.
"It's clear that we are losing an engine customer in 2015 and for Mercedes it is important to have a regular business case so it is important to have at least three customers from 2015 onwards," Wolff told reporters at the Monaco Grand Prix.
"That is why we are having certain discussions with teams and Williams is one of them.
"It would be for 2014. Nobody would sign a one-year deal with anybody," added the Austrian, whose team swept the front row for Sunday's race with Nico Rosberg on pole.
Former champions Williams are currently using engines supplied by Renault, who also supply three other teams including champions Red Bull, but reports have suggested the Mercedes units will be cheaper than the French ones.
Wolff has a foot in both teams, as an executive director of Mercedes F1 and also a shareholder in Williams where his wife Susie is the development driver.
Niki Lauda, non-executive chairman and shareholder in the Mercedes team, and Mercedes Benz high performance managing director Andy Cowell were seen entering Frank Williams' office in the team's motorhome later on Saturday.
Formula One faces the biggest technical changes in decades next year when the current 2.4 litre V8 engines are phased out and all teams must switch to a new 1.6 litre V6 turbocharged unit with energy recovery systems.
Force India have already agreed a long-term deal with Mercedes.
Marussia are looking for a new partner, with Ferrari considered their most likely option, to replace their existing supplier Cosworth while Red Bull's sister team Toro Rosso have said they want to switch from Ferrari to Renault.