Schalke 04 sporting director Horst Heldt has confirmed that the club are interested in signing Matija Nastasic on a permanent deal in the summer.
Nastasic has quickly become a key player in Roberto Di Matteo's side since joining on loan from Manchester City in January, and the Bundesliga club are believed to have an option to secure his services for around £7m.
"There is an option to buy Matija Nastasic that comes into force after a certain amount of minutes he's played, and Nastasic's first weeks in general," Heldt told reporters.
"I always confirmed, and I do so now, that we have an option to buy, but this option is conditioned on several situations which must arise."
Nastasic has made six appearances for Schalke in the Bundesliga.