RING/IBF/WBA/WBO heavyweight champion Wladimir Klitschko has suffered a torn biceps muscle that has forced the postponement of his scheduled Sept. 6 defense against Kubrat Pulev, according to a Monday press release from K2 Promotions.

The bout was to take place at the O2 World arena in Hamburg, Germany, where handlers hope to hold it when it is rescheduled.

“Of course we are all disappointed,” said Bernd Bonte, Klitschko’s manager. “But these things can happen during the preparation.”

Klitschko’s injury was to the left biceps and listed a new date for the bout as “probably Nov. 15,” Bonte stated in the press release.

The postponement is due to “a torn muscle in his biceps” that Klitschko suffered during sparring in the Austria, the release stated, adding that Dr. Robert Siorpaes recommended that Klitschko refrain from training for about four weeks.

“I am very disappointed that the fight can not take place as planned,” said the 38-year-old Klitschko, who was to make his 17th defense against Pulev. “So far I have been in top shape and had a great training camp. I am sorry for my fans as well as my opponent Kubrat Pulev, who has surely prepared just as intensely.”

Klitschko (62-3, 52 knockouts), who stands 6-foot-6 to Pulev’s 6-4, was training in Austria, according to attorney John Hornewer, who e-mailed IBF Championships Chairman Lindsay Tucker notifying him of the development.

Klitschko was last in action for a fifth-round knockout against Alex Leapai, whom he dropped once in the first round and twice in the fifth. Klitschko also holds the IBF, WBA and WBO titles.

The 33-year-old Pulev (20-0, 11 KOs) was last in the ring for his second consecutive stoppage victory, a third-round knockout of Ivica Perkovic in April.

The clash with Pulev is to represent Klitschko’s 26th title fight and the titleholder is 23-2 over that time. Having been beltholder since 2006, Klitschko’s reign ranks second only to that of the legendary Joe Louis, the longest reigning heavyweight champion in the sport’s history. Klitschko’s 23 successful defenses surpassed the 20 by Larry Holmes, the third-longest reigning heavyweight champion.