Deontay Wilder says he still wants to beat Alexander Povetkin despite the postponement of their WBC heavyweight showdown.

American Wilder (36-0-35KOs) was due to head to Moscow this week for the fourth defence of his belt against Povetkin on Saturday, but the fight was cancelled after the Russian failed a drugs test.

Povetkin's sample tested positive for meldonium, a substance that was added to the World Anti-Doping Authority banned list in 2015 and caused Maria Sharapova to be banned, although Povetkin insists he has done nothing wrong.

Wilder, who had been training in Sheffield for the fight, has been left deeply frustrated by the postponement as he was hoping to make a statement with an emphatic victory.

The 30-year-old has also accused Povetkin's team of running scared of him and said he still wants to beat the Russian in the future.

Wilder told Tuscaloosa News that he felt Povetkin has used performance enhancing drugs in the past.

"I think this is definitely not his first time. Even when they banned it, (three) of his tests came back negative and that last test came back positive. Needless to say he was taking it small doses at a time trying to sneak it in. It's not right. What's the crazy part about it that they don't want to admit it, they don't want to man up to the truth. They're still trying to cover it up and make excuses about it. That's not cool," Wilder said.

"I have a lot of friends that are in this sport. I have a lot of friends that know about the human body. One of the things when you take certain substances is the shape of the head. You start seeing the shape of the head change. From how his head was before to how it is now, it's shaped differently. That made us assume that he had to be juicing or something."