West Ham manager David Moyes said England midfielder Declan Rice will not be sold for less than £150m - and is worth "north" of that figure.
Rice, 23, is a reported target for both Chelsea and Manchester United, but the Hammers boss is refusing to sell.
"The first thing to say is that he is not for sale," said Moyes.
"But if you are interested, it will be north of that, because £100m was cheap last summer and £150m just now would be minimum - but he is not for sale."
The Hammers are seventh in the Premier League with only the top four qualifying for next season's Champions League - although they could reach that competition if they win the Europa League, where they are in the quarter-finals.
Rice has been capped 29 times by England and played in all seven of their matches at last summer's Euro 2020 as they reached the final before losing to Italy.
Moyes saw Tottenham reject four bids from Manchester City for England captain Harry Kane last year and says the Hammers would take a similar stance to keep Rice at London Stadium.
"I look at what Tottenham did with Harry Kane, albeit it in a different way," added Moyes.
"They said, 'no, there is a price and if someone wants to pay the price, then we'd probably do it. If they don't then he's not going anywhere'. That's it, they have kept him.
"In many ways, the football clubs are the people in charge, they've got the contracts.
"There will be times when players have got the power, but at the moment we have got Declan on the best part of a three-and-a-half-year contract - just like Tottenham have got Harry Kane on a contract and they control what happens."
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