Tyson Fury said on Wednesday that "size matters" as he counts down to his undisputed heavyweight world title fight with Oleksandr Usyk in Saudi Arabia next month.

The clash in Riyadh was rescheduled for May 18 after it was postponed because the British boxer suffered a cut in training earlier this year.

Usyk holds the WBA, IBF and WBO heavyweight belts while Fury is the WBC champion.

Former undisputed cruiserweight champion Usyk has won all of his 21 professional bouts, while Fury has 33 victories and one draw on his record.

The Ukrainian, 37, won his heavyweight titles by beating Britain's Anthony Joshua in 2021 and has defended his belts twice, including in an August 2022 rematch with Joshua.

"I've seen some stuff in the media that this is really personal between me and Oleksandr Usyk," Fury said at a press conference in his home town of Morecambe, in northwest England.

"This is not personal; it's strictly business for both fighters.

"There's a lot of stuff on the line but I don't hate him and he doesn't hate me. He's a good husband, good God-fearing man, so I respect him," he said.

Fury, 35, stands 2.06 metres (six feet, nine inches) tall -- 15 centimetres taller than his opponent, and he believes that will count in his favour.

"When the cruiserweights step up to the big boys, usually they get found wanting... you can beat the average big ones but you can't beat the elite big ones because size really matters," he said.

"We have weight divisions for a reason and he's going to be found wanting when he fights me on May 18."

Fury, who had a split-decision win over former mixed martial arts champion Francis Ngannou in October, wants to stamp his authority on the heavyweight division.

"If Tyson Fury can't beat Usyk, Tyson's no good, end of," he said. "I'm not going to pull any punches, it is what it is."

He added: "This is my time, my destiny, my era and my generation. Fact."

Fury's promoter Frank Warren said he expected Fury to win in "explosive style", picking out what he believes to be Usyk's Achilles' heel.

"He doesn't like it to the body, that's for sure, and for me the biggest exponent of exploiting a boxer's weakness is the professor here (Fury) and that's what he does.

"If anybody's going to exploit it, it's going to be Tyson. He's got the mental capacity to do that and keep doing what he has to do.

"I genuinely believe that Tyson will win this fight in explosive style." (AFP)