Borussia Dortmund CEO Hans-Joachim Watzke insists it is down to the German club where Manchester United target Mats Hummels plays his football next season.

Reports in British media suggest United are poised to table a 35-million-euro (£25.7m, US$38.1m) bid for the 2014 World Cup-winning centre-back, who has admitted the Red Devils would be his "only" choice if he moves abroad.

"Nothing has been decided yet, we (Dortmund) will have a discussion in the next few weeks and see what happens," Hummels told Sky Sports after tenth-placed Dortmund's 1-0 defeat at home to run-away league leaders Bayern Munich on Saturday.

But with two more years to run on his current contract, Dortmund are eager to keep their 26-year-old captain having watched top talent Robert Lewandowski and Mario Goetze leave for rivals Bayern Munich in the last two seasons.

"We have had the situation in Dortmund recently that we have lost one of our top performers every year," Watzke told German daily Bild.

"And we still haven't stopped playing football.

"But to make it clear, Mats Hummels knows the contract situation.

"The decision as to where Mats plays next season is of course only down to Borussia Dortmund."

Having won the 2011 and 2012 German league titles, then finished runners-up to Bayern for the last two seasons, Dortmund have struggled for domestic form this season.

They found themselves bottom of the league at the start of February before exiting the Champions League at the last-16 stage. They are now 15 points off a Champions League berth for next term.

They are also waiting on Germany midfielder Ilkay Gundogan to extend his current contract, which expires in June 2016, "but no decision has yet been taken", added Watzke.

"No one needs to worry: we will have a strong team next year," he said.

"If we don't qualify for Europe next season, we will have to trim down, because our squad will be too big for a year without international competition.

"But the team budget will still be higher than in the years when we were German champions."

One player reported to be poised to leave Dortmund at the end of the season is Italy striker Ciro Immobile, who has failed to make an impact since his 18.5-million-euro move from Torino last year.