NEW YORK (AP) — Heavyweight boxer Deontay Wilder and promoter DiBella Entertainment have filed a $5 million lawsuit against Russian Alexander Povetkin and his promoter.

Wilder and DiBella filed suit alleging breach of contract Monday in U.S. District Court of New York. Wilder, the WBC champion, and mandatory challenger Povetkin were scheduled to fight May 21 in Moscow but the fight was postponed indefinitely when the Russian tested positive for meldonium.

The banned substance is a blood-flow drug that historically was used to improve Soviet soldiers' endurance.

The suit seeks damages of no less than $5 million and names Povetkin and promoter World of Boxing LLC, run by Andrei Ryabinsky. YahooSports first reported the suit.

Wilder was scheduled to make $4.369 million for the fight. He'll face Chris Arreola July 16 in Birmingham, Alabama.

In a Twitter post Monday, Ryabinsky said: "There will be several of our lawsuits at the start of next week. It'll be a real rumble."

The suit said Povetkin was tested three times in early April, but didn't test positive for the drug until April 27.

Wilder's camp became concerned that Povetkin might be doping in late March, calling it "highly suspicious" that Povetkin had traveled to Spain, the suit said. Spain, according to the suit, is not traditionally regarded as a place for boxers to train but "is notorius as an epicent of doping."

Ryabinsky had earlier predicted the Wilder-Povetkin fight "should take place by the end of the year." Wilder's promoter Lou DiBella opposes talk of rescheduling before a WBC ruling.

Tennis star Maria Sharapova is appealing a two-year ban after testing positive for Meldonium.