Bernd Boente has hinted that heavyweight world champion Wladimir Klitschko could pull out of his scheduled fight with Alexander Povetkin due to drug testing.

After two previous cancellations on behalf of the Russian, a fight was finally signed after Povetkin's victory over Andrzej Wawrzyk last month.

However, a row has erupted regarding the drug testing, with the Ukrainian - holder of the WBO, IBF and IBO, WBA Super belts - adamant on Germany's National Anti-Doping Agency (NADA) doing the pre-fight testing. However, the WBA World champion wants to use an agency from his own country.

Boente, Klitschko's manager, said that drug testing is not the only issue with regards to the fight going ahead as planned on October 5.

"There are still huge gaps in the contracts, not only in terms of the drugs testing," Sky Sports News quotes him as saying. "Better safe than sorry. I've already seen too much in this business."

The fight is due to take place at the Olimpiyskiy in Moscow.