Alexander Povetkin was set to fight Deontay Wilder for the WBC title

Heavyweight contender Alexander Povetkin has failed a drugs test ahead of his world title fight against Deontay Wilder.

Povetkin (30-1 KO 22) was due to fight the WBC world heavyweight champion (36-0 KO35) at the Megasport Arena in Moscow on May 21.

But his clash against Wilder has been put in jeopardy after he tested positive for the banned substance meldonium.

The Russian's promoter, Andrei Ryabinsky, told news agency TASS: "We're in contact with the WBC. They'll take the decision on whether the fight will happen or not."

Wilder's fight against Povetkin is now in doubt

Meldonium - the same drug found in tennis star Maria Sharapova's sample at the Australian Open - was added to the banned substance list by the World Anti-Doping Agency in September and came into effect on January 1, 2016.

Ryabinsky added that Povetkin did take meldonium last year, but stopped before it was banned, and only "leftover traces of meldonium at a very low concentration" were found in a blood sample given by the 36-year-old last month.