Schalke "cannot do any more" to convince midfielder Leon Goretzka to stay beyond next summer, sporting executive Christian Heidel has said.

Goretzka, 22, is out of contract at the end of June and both Sport Bild and Marca have reported that he has opted to join Bayern Munich at the end of the season.

His agent Jorg Neubauer has denied the reports and said the Germany international, also linked with Real Madrid, Barcelona and Liverpool, has yet to make a decision on his future.

Heidel said second-placed Schalke would not increase their offer for Goretzka to extend his stay -- believed to be in the region of €12 million per year.

He told Funke Mediengruppe: "It will not be long before a decision is announced, and it will not drag out until the end of January.

"Schalke cannot offer any more nor do any more than we already have.

"Leon wanted to wait and see how Schalke's sporting development went. It's been six months.

"We are in the best possible position in the league table behind Bayern and have reached the DFB Pokal quarterfinals."

In May, Sport Bild reported that Goretzka had already agreed to join Bayern -- a claim denied by the midfielder on his Facebook page.