West Ham forward Marko Arnautovic "is not for sale" - despite the player's agent and brother saying he wants to move to a Chinese club.
The Hammers have received a £35m bid for the Austrian from an unnamed side in China.
The 29-year-old has scored seven Premier League goals this season.
His agent and brother, Danijel Arnautovic, told Talksport on Thursday it is his client's "great desire that West Ham accept the offer from China".
A West Ham spokesperson said: "Marko has a contract and we fully expect him to honour it. He is not for sale."
Arnautovic moved to London Stadium for a club-record £20m fee from Stoke in July 2017 and his contract runs until 2022.
A club, believed to be Chinese champions Shanghai SIPG, is understood to have bid £35m for Arnautovic with wages understood to be £200,000 a week over a four-year contract.
Danijel Arnautovic added: "West Ham bought Marko for peanuts. They paid £20m for him, which is nothing in the current market.
"They bought him to keep them in the Premier League last season and he did that. He took every award at the club; best player, signing of the season and the players' award.
"Now West Ham have a fantastic offer. It is close to double what they paid for him.
"He wants to go to a new market and challenge for titles."
At a news conference on Thursday, West Ham boss Manuel Pellegrini admitted it could be difficult to keep the forward in the future.
"Those are all rumours," said the Chilean. "We know we have a very good player in Marko, a lot of clubs may want him to play for them. At the moment we have no news about him.
"I don't want to talk about things that might happen. Marko in this moment is a player of our team, players of his quality and other players like Declan Rice, Felipe Anderson, other clubs will want them but that is one thing. I don't think they will go.
"I want to keep him, of course, but you never know what might happen in the future."
West Ham, 10th in the Premier League, host fifth-placed Arsenal on Saturday (12:30 GMT) and Pellegrini expects Arnautovic to play.
"Marko and all the other players involved in rumours have their heads here," added Pellegrini.
"They want to continue playing the way they have been so far and I am sure he will have his head in the game against Arsenal."