Stefan Kiessling has been struggling with injuries. Oliver Kremer at Pixolli Studios/Getty Images

Bayer Leverkusen forward Stefan Kiessling has admitted he may soon be forced to retire due to a persistent hip injury.

The 32-year-old signed a new contract through to 2018 earlier this year but he has raised doubts as to whether he will be able to see that out due to his chronic injury problem.

"It might happen [that I retire]," Kiessling told the Rheinische Post newspaper. "If the pain becomes too much and I realise that I have to sit out often, then I would have to be honest with myself and say that it no longer makes any sense.

"If that were to be the way things would end, then certainly it's not the kind any professional footballer wants, but I am not thinking at the moment about that being the case."

Kiessling has been struggling with the hip injury, which deteriorated after a fall in a Europa League clash with Sporting Lisbon in February, throughout preseason and he is currently training separately from his teammates.

He is making progress, though, and hopes to be back in full training come the second half of the month in time for the start of the Bundesliga season.

"I'm not giving up hope, particularly not now I can see progress being made," he said. "I am giving everything to make sure my career doesn't come to a stupid end, but if the time does come when it no longer works, then I won't be angry."