Chelsea transfer target Kai Havertz has an agreement with Bayer Leverkusen that he can leave this summer, according to the club's sporting director Rudi Voller.
But certain conditions have to be met if the 21-year-old is to be sold, former Germany striker Voller has said.
Havertz is believed to be on Chelsea boss Frank Lampard's shopping list this summer after impressing in the Bundesliga this season, with Manchester United also reported to be interested.
The West London club have already signed Timo Werner from RB Leipzig and and Hakim Ziyech from Ajax for a combined £89million.
But Havertz could cost almost as much again, with the attacking midfielder valued at £75m-plus.
And Voller has admitted that a summer transfer could be a possibility - although with Havertz's contract not due to expire until 2022, he suggested the young Germany international owed Leverkusen some loyalty.
"We have an agreement - if it fits, he can go this summer," Voller told German publication Bild.
"As of now, he is a player of ours. We have our ideas, we know what he can do. I personally hope that he stays one more year.
"Of course, you can't force anyone. Havertz knows what he owes to his colleagues, the fans and the club."
Bayer missed out on Champions League qualification by two points, and Voller has conceded that not being in Europe's top competition could increase the club's chances of losing Havertz.
Bayern Munich have claimed they cannot afford the midfielder, who was rumoured to have been left out of Bayer's defeat to the Bundesliga champions last month because of Chelsea's interest.
Voller denied that was the case, saying: "Regardless of whether it's [the] Europa League or Champions League or if it is wanted by the players [and clubs], I couldn't understand if a player didn't want to [play]."
Chelsea are expected to step up their attempts to sign Havertz once Saturday's German Cup final between Leverkusen and Bayern is out of the way.
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