Borussia Dortmund are facing up to the possibility of losing two key players this summer after the agent of Robert Lewandowski claimed a deal is being worked on for the Poland international to leave the Westfalenstadion.

Lewandowski scored all four goals as Dortmund thrashed Real Madrid 4-1 in the first leg of their Champions League semi-final last night but much of the post-match talk centred around his future.

His contract expires at the end of next season, leaving Dortmund in the unenviable position of having to decide whether to cash in this summer of risk seeing the 24-year-old leave on a free in 2014.

Reports in Germany today suggest they have opted for the former with the player's agent Maik Barthel suggesting Dortmund have sanctioned his departure.

"We have reached an agreement with a club and intend (him) to move this summer," Barthel told Sport Bild.

"There is a very interesting offer for Robert which fulfils entirely the demands set by Dortmund and also the demands of Robert.

"Dortmund have assured us that Robert can move at the end of the season under these conditions.

"We stick to agreements and now it's up to the clubs to sort things out."

Barthel stopped short of naming the club in question but speculation suggests it is Bayern Munich, who earlier this week agreed to activate the 37 million euros release clause of Dortmund playmaker Mario Gotze.

Losing two of their best players to their closest domestic rivals would be a major setback for Dortmund, who are also likely to meet Bayern in the Champions League final after the Bavarians' 4-0 hammering of Barcelona on Tuesday night.

"We are getting 37 million for Gotze which we don't even want," said coach Jurgen Klopp, echoing the words of his club's general manager Hans-Joachim Watzke, who said he could "do without" a transfer fee for Lewandowski, as long as he stays for another year.

Watzke added on Sky television: "Our wish is explicit that he stays here.

"It all surprises me," said Watzke. "We are willing to do without a transfer fee for him (if he leaves as a free agent in 2014).

"I have had plenty of wishes in my life which have come true."

Gotze and Lewandowski combined for Dortmund's opening goal against Madrid last night before the former Lech Poznan striker took centre stage, netting three more times to leave Jose Mourinho's men with an uphill task at the Bernabeu next week.

His performance was no surprise given his record this season. He has scored 34 goals in 42 games and has netted in each of his last 12 Bundesliga appearances.