Deontay Wilder says Oleksandr Usyk is "no threat" to him as the Ukrainian is "too small" to be a major heavyweight force.
Cruiserweight king Usyk will face Chazz Witherspoon in his first heavyweight fight in Chicago on Saturday.
Usyk this week stated a bout with Wilder is the one he wants most, but the WBC champion does not believe the 32-year-old is big enough to ruffle feathers in the heavyweight division.
"He's not a threat to me," the American told Sky Sports. "He's too small for me. He does a lot of movement but that doesn't faze me."
Wilder warned his rivals he is becoming a better fighter as he prepares to face Luis Ortiz in Las Vegas on November 23, with a rematch against Tyson Fury potentially to come next February.
When asked who his biggest threat is, Wilder said: "Myself. I have something that I've been blessed with. It lasts from the first to the 12th - it never goes away.
"People may think I'm fatigued or out of it but, if you get hit, there are repercussions to be paid. It's amazing because I don't even know the strength of my own power.
"I hold my fiancee's hand and she says, 'Baby, you're squeezing me too tight'. I am very heavy-handed.
"I'm only getting better with my technique. One thing, out of everything, that I've been working on is my technique. From point A to point B with speed.
"The speed is the power but I already have the power. So when all that comes together, when lightning and power transfers from point A to point B? Bam, baby. Goodnight."