Swansea City's owners insist the club will not be "bullied" into selling midfielder Gylfi Sigurdsson.
Everton are reportedly eager to sign the Iceland international but are said to have seen a £40million bid rejected, with Paul Clement's side holding out for £50m.
Sigurdsson did not travel with the squad for their pre-season tour of the United States, with Swansea stating that the 27-year-old "did not feel in the right frame of mind" due to the speculation over his future.
However, the Swans' American owners, Steve Kaplan and Jason Levien, have now warned potential suitors that they can forget about signing Sigurdsson unless they meet the club's asking price.
"We are disappointed Gylfi has taken the decision not to join his team-mates in America where they are working with the coaching staff to prepare for the upcoming season," they said in a statement published by Wales Online.
"At this time we have not received an offer from any club which represents a fair valuation of Gylfi given his importance to our club.
"As we have stated, we will not be bullied or forced into a decision until a club meets our valuation of the player, no matter whether they believe they have an agreement with the player. Any such agreement would obviously be in contravention of Premier League legislation.
"We have the ultimate respect for Gylfi as a person and a player and we are optimistic that he will reconsider his decision and join his team-mates."