Borussia Dortmund have admitted that the future of Ilkay Gundogan and Mats Hummels is still not clear amid strong interest from Manchester United.

The German duo have been heavily linked with a move to Old Trafford in the summer, owing to the Bundesliga club's poor season, and it has intensified in recent weeks following the announcement of manager Jurgen Klopp's departure from the club.

Gundogan will be entering the final year of his contract at the end of the current campaign and has yet to pen a new deal with the club, with reports suggesting that Louis van Gaal's side are close to completing a deal for the all-action midfielder.

But the German club have completely denied talking to the 20-times English champions and sporting director Michael Zorc added that the player himself has not yet made a decision on whether to extend his deal or not.

United, however, were given hope with chief executive Hans-Joachim Watzke indicating that he will discuss Gundogan's transfer, if the player declines the offer of a contract extension.

"Gundogan's situation isn't straightforward, because his contract expires in 2016. There will be a decision soon," Zorc said, as quoted by the Manchester Evening News.

"If Ilkay tells us he doesn't want to extend, then we'll sit down and discuss it. But that hasn't happened yet," Watzke added.

Hummels, on the other hand, has a contract until 2017 and the club has confirmed that they have not received any offers that they can consider for the World Cup wining defender.

However, the Bundesliga club's sporting director does foresee some changes at the club in the summer, but has made it clear that there will not be wholesale changes made to the team.

"As far as I know, Hummels' contract still runs until 2017. We did not receive any offer that we should think about.

"There will surely be some changes to the team this summer. Maybe more changes than in recent years. But we won't radically change our team," Zorc confirmed.