MANCHESTER -- Jose Mourinho is keen for Manchester United to tie up a new contract for Marouane Fellaini before the end of the year, sources have told ESPN FC.

Fellaini's current deal is set to expire at the end of the season and if United cannot reach another agreement before Jan. 1, the 29-year-old will be free to sign a pre-contract with another club.

Mourinho wants to keep the Belgium international at Old Trafford, while sources have told ESPN FC that the former Everton man is happy at United.

There is, however, a fear that a lucrative offer from Turkey or China could change things, especially with Fellaini due to turn 30 in November and, in theory, negotiating his last big contract.

Marouane Fellaini is out of contract at the end of the season. Michael Regan/Getty Images

Tentative interest in the midfielder from Galatasaray in the summer was blocked by Mourinho, who said at the time it would be easier for the Turkish side to appoint him as manager.

The United boss has since said his squad is "weaker" when Fellaini is not available, adding that he is "much more important than what you can imagine."

Fellaini, who joined United from Everton for £27.5 million in 2013, made 47 appearances under Mourinho last season, bettered only by Paul Pogba, Ander Herrera and Marcus Rashford.

He signed a four-year deal, with the option of an additional year, when he arrived from Everton under former manager David Moyes.

United triggered their option in January to keep Fellaini at the club until the end the 2017-18 season and, at the time, to ward off strong interest from the Chinese Super League.