Dillian Whyte has described Deontay Wilder as an "embarrassment to heavyweight boxing" after the WBC champion rejected a fight offer.
The Brixton man is hoping to secure a world title fight this year, but Wilder posted an expletive-laden response on social media after promoter Eddie Hearn put forward a deal for a WBC title defence against Whyte.
Four victories have lifted Whyte up the rankings since his first defeat to Anthony Joshua and the 29-year-old believes he must become a mandatory challenger to force a fight with one of the champions.
"In this game, nobody's going to give each other anything, you have to go after it yourself," Whyte told Sky Sports.
"Guys like Deontay Wilder are an embarrassment to heavyweight boxing. All the great champions have losses on their record because they fought other great fighters and that's the problem with Deontay Wilder, his last 10 fights have been with nobody.
"We have offered him five times more money than he made for his last fight, but he doesn't want to fight, so what's the problem?
"Why's he avoiding? Because he knows I'm dangerous and he knows that he'll lose the fight."
Whyte can boost his profile in America when he makes his US debut on the undercard of Terence Crawford's world title unification clash against Julius Indongo on August 19, live on Sky Sports, with an opponent yet to be announced.
"It's a big show, it's a massive card," said Whyte. "I think it's the first full unification fight in about 20 or 30 years, all of the belts on the line, Terence Crawford against Julius Indongo, so I'm very excited about it.
"We're trying to get the Deontay Wilder fight, so it'll be good for me to get some exposure in the USA and get some experience abroad as well."