West Ham have insisted Marko Arnautovic is not for sale after his agent claimed the Austrian forward wants to move to China.
A Chinese Super League club, believed to be champions Shanghai SiPG, are understood to have launched a STG 35 million ($A62 million) swoop for Arnautovic, the Hammers' top scorer.
The club will attempt to lure Arnautovic, who turns 30 in April, with wages understood to be STG 200,000 a week over a four-year contract.
Arnautovic's brother Danijel, who also acts as his representative, revealed that the player wants to leave and urged West Ham to sell.
But a Hammers spokesperson said: "Marko has a contract and we fully expect him to honour it. He is not for sale."
Manager Manuel Pellegrini had earlier said he was determined to keep Arnautovic, who has scored eight goals this season, including three in his last two matches.
But Danijel Arnautovic, who has agitated for a move for his brother before, issued a statement in which he claimed the striker has a "great desire" to go to China.
"He knows the West Ham fans love him and he has a special connection with them, but things move on, this is the world of sport and he hopes they can understand.
"Until he is no longer a West Ham player, he will give everything to the club. He hopes the fans can respect his wishes," the statement read.
Pellegrini, who substituted Arnautovic against his will after only 20 minutes in Saturday's FA Cup win over Birmingham, had earlier shrugged off the speculation.
"Those are all rumours," Pellegrini said. "We know that we have a very good player in Marko, a lot of clubs may want him to play for them.
"I don't want to talk about things that might happen. Marko in this moment is a player of our team. I want to keep him, of course, but you never know what might happen in the future."