Felipe Massa 'agrees' to come out of retirement as Valtteri Bottas set to replace Nico Rosberg

Massa announced his retirement in September but is set for a U-turn

Williams hinted they would let Bottas leave if Massa returned (Getty)

Felipe Massa has reportedly agreed to come out of retirement to rejoin Williams next season, if Valtteri Bottas departs to replace the retired Nico Rosberg at Mercedes.

The 35-year-old Brazilian announced his retirement in September and brought the curtain down on his 14 years in Formula One at the end of the 2016 campaign, but now seems set for a U-turn.

Williams hinted last week that they could let Bottas join Mercedes in 2017 if they could tempt Massa back.

Deputy team principal Claire Williams told BBC Sport: "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."

Reports in Italy, Brazil and Britain on Tuesday evening claimed Massa has indeed been persuaded to reverse his retirement decision, with the matter now dependent on Bottas' next move.

Mercedes have had one offer for 27-year-old Bottas turned down as they search for a replacement for Rosberg.

Rosberg, 31, shocked the sport when he decided to retire just five days after being crowned champion and it remains to be seen who will fill the German's boots to team up with Lewis Hamilton for 2017.

Earlier on Tuesday, Mercedes non-executive chairman Niki Lauda insisted his team were yet to make a decision on Rosberg's replacement and said they may wait until the end of January before making an announcement.

Meanwhile, Williams have announced chief technical officer Pat Symonds will step down from his role - with rumours persisting that Paddy Lowe of Mercedes is set to fill the void.

Mercedes have already had one bid for Bottas turned down by Williams (Getty)

Symonds has been with the British team since 2013 but is now leaving at the end of the year.

The 63-year-old, who had a storied history in F1, arrived at Williams from Virgin Racing in the middle of the 2013 season, helping the team to third in the constructors' championship in his first full year.

Lowe, the technical executive director of reigning champions Mercedes, is widely reported to be close to a switch to a senior technical role at Williams.