Mercedes will not name Nico Rosberg's replacement until January, the team said on Thursday, amid reports they are chasing Valtteri Bottas from Williams.
It comes with French media saying Felipe Massa is in talks with Williams about reversing his decision to retire, which would free up 27-year-old Bottas to switch to Mercedes.
"There will be no announcements from us until next year and nothing is planned for the period between now and our return to work on January 3," Bradley Lord, head of the Mercedes team communications, said in a WhatsApp message to reporters.
The delay will ramp up speculation about who will take the vacant seat alongside Lewis Hamilton at Mercedes following world champion Rosberg's shock retirement earlier this month.
Reports in Britain and elsewhere say Mercedes want flying Finn Bottas -- whose best season came in 2014 when two runners-up spots helped him to finish fourth overall -- to step into Rosberg's racing boots.
Williams all but confirmed this later on Thursday as the deputy team principal Claire Williams told the BBC Bottas could leave but only if they could secure the services of an experienced driver such as Massa.
"I'm delighted to see that a team like Mercedes lists Valtteri as a potential replacement for Nico," said Williams, who is team chief Frank's daughter.
"We have always known Valtteri is one of the sport's key talents and are proud that the championship leaders recognise this.
"However, Williams has its own ambitions and we must always ensure we give our team the best opportunity to move forward. Any changes would only be made if Williams remains in a strong position to compete and develop in 2017.
"If we did allow Valtteri to leave, we would only do this if an experienced, credible alternative was available, such as someone like Felipe Massa, for example.
"Whatever we decide, it must be in the best interests of this team," added the 40-year-old.
Massa, 35, retired from Formula One at the end of the season last month, but French sports daily L'Equipe on Thursday said he was in talks for another year with Williams.
One of the two seats at Williams has already been taken by rookie Lance Stroll, 18.