Clubs hoping to sign Pierre-Emerick Aubameyang only have a few days to open talks with Borussia Dortmund, says Hans-Joachim Watzke.
Last season's Bundesliga top goalscorer is reportedly being pursued by Chelsea and AC Milan, though he is expected to cost around €80 million.
Despite the ongoing speculation, Dortmund CEO Watzke says there have been no offers for the 28-year-old and the window for them is closing.
"We have not had any offers," he told Welt am Sonntag. "We will wait a few more days but not long anymore.
"We have told Aubameyang: 'if you want to move and have a club ready to meet our conditions, come to us and we can will talk about it'. But we also explained that this is only possible within a certain window of time. We must find a replacement, which is difficult, if not impossible.
"Personally, I would prefer he stay with us, but there are a few clubs on this planet where he can obviously earn more."
While Aubameyang's future remains uncertain, Dortmund are optimistic about Mario Gotze, who made his first appearance since February in Saturday's friendly against Urawa Reds.
The Germany international has recovered from a metabolic disorder and Watzke says he is ready to play an important role next season.
"From his mentality and attitude to his great passion, Mario was always ready," he said. "That was never a concern. However, he suffered a serious illness. We have never talked about it in detail and will not.
"[Sporting director] Michael Zorc and I had very close contact with him over the last five months. We knew everything. The fact that it is now all going in the right direction makes us all happy.
"If Mario is fit, he is one of Borussia Dortmund's most important players.""We have told Aubameyang: 'if you want to move and have a club ready to meet our conditions, come to us and we can will talk about it'. But we also explained to him that this is only possible in a certain time window which closes so slowly. We must finally provide for a replacement, which is difficult or impossible. Personally, I would prefer him to stay with us. "