Kostya Tszyu has been stripped of his World Boxing Association (WBA) belt, the WBA confirmed.

The WBA's US-based legal counsel, Robert Mack, said he faxed a letter to Tszyu's manager, Matthew Watt, in Sydney informing the Russian-born Australian boxing champion he would lose his super-lightweight title.

"My letter constitutes a decision to vacate it," Mack said.

Watt told AAP in Sydney he was waiting for official word before considering an appeal: "It's a shame that is what is going on, and Kostya may well appeal it, but we just need to hear officially from the WBA their position."

Tszyu has been struck by two serious injuries in the last 12 months - shoulder and Achilles - and was unable to defend his WBA belt.

Rival boxing promoters have argued Tszyu - who at one stage held the WBA, IBF and World Boxing Council (WBC) belts in the division - did not make a mandatory defence of his WBA belt for more than three years.

After a review of the circumstances, Mack said it was decided Tszyu should be stripped because of his inactivity.

"We just felt the period is up," Mack said.

The letter sent to the Tszyu camp says the boxer can appeal the decision.

"This letter, therefore, confirms the decision of the WBA to vacate the title in question," Mack wrote in his letter to Watt.

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