Bayern have made it through to the semi-finals of the Champions League, where they will play Lyon, while Hamburg meet Fulham in the last four of the Europa League.

Should either club progress to the next stage, it will mean their players won't be free to join up with the Germany squad until mid to late May, meaning they will miss the first warm-up game against Malta on May 13.

"The later I have all the players, the more difficult it will be to bring them to a similar level as they will need individual training," Low told the Bild newspaper.

"But the Bayern and Hamburg players will still be getting intense training (with their clubs) as no-one wants to drop off.

"It is problematic that eight to 10 players will be missing at the start of our World Cup preparations.

"In the weeks leading up to the World Cup, we need to be flexible. We will have to perform a balancing act to see which players need to do more and which ones need to do less."

The Malta game will also come too early for players from Werder Bremen, who meet Bayern in the DFB-Pokal final in Berlin on May 15.

"I know I will have problems for the Malta match," he added.

"But it was to be expected that Bayern or Bremen, or maybe even both, would reach the final."

Low is not concerned, however, that some of his squad are not firing on all cylinders currently.

He added: "I think of (Bastian) Schweinsteiger in 2006 or (Lukas) Podolski in 2008 who were not in top form. But they went on to have strong tournaments.

"I am not worried but the situation is potentially serious. Our task is to get the players in top form in a short space of time."

Low played down concerns over captain Michael Ballack, who has lost his place in the Chelsea side in recent weeks.

"Michael told me has had a cold and then a problem with his Achilles tendon, so he could only train irregularly," he said.

"But he is back now. I don't see a problem with him. We talk regularly and will fly again to England to visit him."