Bayern Munich have told Tottenham they want a decision by the end of Friday over whether they are prepared to sell England captain Harry Kane.
The deadline is a signal that Bayern are growing frustrated with the current situation, although it is not clear if they would then walk away from any deal if it was not met.
Tottenham have refused to comment.
Kane, 30, is Spurs' all-time top scorer but has one year left on his contract.
There has been no suggestion Kane would be willing to extend his contract, so if Tottenham chairman Daniel Levy opts to keep the England striker it would effectively be ending the club's last chance to cash in on their talisman.
Bayern officials met Levy earlier this week but no agreement was reached.
Tottenham open their Premier League campaign at Brentford on 13 August. Bayern begin their season with a German Super Cup meeting with RB Leipzig a day earlier.
The transfer window does not close until 1 September, but it is felt all sides would prefer a resolution before the new season begins.