Aussie boxer Alex Leapai has compared himself to Mike Tyson, saying Ukrainian great Wladimir Klitschko won’t cope with his power in their world title bout.

Queensland underdog Alex Leapai has likened himself to Mike Tyson and boldly declared Wladimir Klitschko’s long reign at the top of world heavyweight boxing is about to end.

Leapai, the Samoan-born delivery truck driver and ex-con, is supremely confident heading into one of the biggest bouts in Australian boxing history, claiming he would shatter the Ukrainian’s “glass jaw”.

Easily the biggest pay day of the born-again 34-year-old’s largely-unheralded career, he will face Klitschko in the unified world title fight on April 27 (AEDT) in Germany after signing the contract in Brisbane on Tuesday morning.

Leapai, known as ‘Lionheart’, set up the showdown when he stunned the boxing world by defeating Russian Denis Boystov in November to become the top WBO contender.

The father-of-six has been written off by pundits and bookmakers around the globe but Leapai and trainer Noel Thornberry said the Ukrainian great’s 61-3 (51 KOs) record – seeing him dominate the division for a decade – counted for naught.

The pair claimed Klitschko, unbeaten for the past decade, had bolstered his record in recent times with a string of soft opponents who let him bully them by standing off.

Leapai (30-4-3 24 KOs) also pointed to the 37-year-old champion’s three losses – all TKOs against Lamon Brewster, Corrie Sanders and Ross Puritty – saying none packed the same heat as his punch.

“Klitschko has a glass jaw,” he said. “He can get fired up but on the night we’re going to bring it home.

“I don’t believe this guy has faced anybody with the power that I’ve got.

“It ain’t going the distance. I promise you one of us is going to be knocked out, but it isn’t going to be me.”

Defending the WBA, IBF, WBO and IBO belts against Leapai, Klitschko holds a 15cm height advantage but the challenger promised to get inside and go to town.

“Tyson was only a short fighter and he dominated for so many years. He had the power and I’ve got the power too,” he said.

“I’ve watched his last 10 fights. A lot of the guys who have fought him just don’t have a dig. For me, it’s not about the money.”

Even before his tough talk, Leapai’s points victory over Boystov had Klitschko on guard.

“I am wary, but I will prepare myself as well as I can and I’m looking forward to a great challenge,” he said after two months of negotiations were finalised.

Leapai promised the $1.5-$2 million fight won’t change him as a person, having already turned his life around as a Christian after being jailed for assault.

Thornberry said Leapai would continue his preparations in Queensland and only travel to Germany a week before the bout in Oberhausen.