Williams are prepared to release Valtteri Bottas to become Lewis Hamilton’s Mercedes team-mate in 2017.
Mercedes want the Finn, 27, to replace Nico Rosberg, who retired after winning the world title last month.
Deputy team principal Claire Williams told BBC Sport the team would let Bottas leave “if an experienced, credible alternative was available”.
Williams suggested Felipe Massa could return, despite retiring at the end of this season.
would not make an announcement on Rosberg’s replacement until at least 3 January.
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Bottas one of five options?
Three-time British world champion Hamilton will be consulted about German Rosberg’s replacement, but the final decision will be Mercedes’.
“Basically, once they’ve dwindled it down to five drivers – or whatever it is, the shortlist – contractually they have to discuss with me,” Hamilton, 31, told Channel 4.
“But I don’t have a say who it is.”
Massa to make Williams return?
Williams need an experienced driver for 2017 to partner the 18-year-old Canadian rookie Lance Stroll, who is making his debut and is said to be bringing financial backing worth as much as £20m.
Re-employing Massa could be a good solution for Williams. Although he announced his retirement from F1 in September, the Brazilian made it clear he wanted to continue racing. So a seat at Williams could be a good opportunity for him.
And it could provide a benefit for Williams because the team could use the money it saves on the engine fee and Bottas’ salary to fund technical developments and boost their competitiveness in future years.
Sources say Massa made his announcement only after he realised that Williams were going to keep Bottas and sign Stroll and that he was unable to find a similarly competitive car elsewhere.
Wolff’s first offer to Williams for Bottas was for a reduction of 10m euros (£8.4m) in their engine bill.
It is considered likely that Williams will hold out for a figure much closer to the full amount – 17m euros (£14.2m) – to release the driver.
They are aware that Mercedes have money available for the deal because they no longer have to fund Rosberg’s salary – which was set to be in the region of $22m (£17.6m) for each of the next two years.
In a separate deal, Mercedes executive director (technical) Paddy Lowe is poised to join Williams in a senior management role.
Mercedes are set to replace him with the former Ferrari technical director James Allison.