The 28-year-old has been reported to want to leave the Barclays Premiership club, although Chelsea have offered him a four-year deal to stay.
A statement from Chelsea read: "William Gallas has made a great contribution to Chelsea since he has been here and he has been offered a very good new contract in recognition of that.
"That contract is still on offer and we would like him to be at Chelsea for the next four years.
"If it is not accepted, then William is still under contract for one more year and we will not be encouraging offers for players that we want to keep.