Ross Brawn has admitted that he faces a difficult decision over whether Michael Schumacher will remain at Mercedes beyond the end of this season.
Reports late on Thursday night suggested that Lewis Hamilton was ready to agree a move to Mercedes, throwing Schumacher's future further into doubt.
Team boss Brawn told Radio Five Live: "The decision for Michael to stay or not continue is a difficult one.
"Obviously he's very involved in that decision, and discussions are ongoing at the moment.
"Michael has been a huge asset to the team, he's really taken us forward. I do think Michael contributes an awful lot."
A number of Mercedes officials are reportedly eager for Schumacher to retire.
