You're no Kostya, Tony Harrison warns Tim Tszyu

Tony Harrison has ceased the play acting and warned Tim Tszyu he didn't travel across the globe to take a beating.

The American showman has been all kiss and cuddles towards Tszyu in the lead-up to their looming world title showdown in Sydney, but finally showed his game face on Thursday.

The only man to conquer countryman Jermell Charlo, who holds all four belts in the super-welterweight division, insists Tszyu is way out of his league taking such a high-risk fight.

The winner will claim the interim WBO strap and face Charlo later in the year with a chance to be crowned the undisputed world champion.

That was already on the table for Tszyu had he waited for Charlo to recover from two broken bones in his left hand so their postponed January blockbuster could be rescheduled.

"Ten. F****** 10," Harrison said when asked how many levels Tszyu will be stepping on March 12 at Qudos Bank Arena.

"Like I am the only fighter that was a world championship fighter that he's fought.

"He hasn't fought a world championship fighter yet. I am the first one - and I am probably going to be the last because he's going to go back to the bottom and has to rebuild this stuff back up."

Tszyu (21-0, 15KO) is bidding to join a select band of father-son boxers to win world titles, including the legendary Julio Cesar Chavez and Julio Cesar Chavez Jr and Leon and Corey Spinks.

Harrison (29-3-1, 21KO) respects the 29-year-old for his toughness and resilience.

"He's not a weak kid but to say he's like Kostya Tszyu, I think we're giving him just a little too much," the Detroit fighter said.

"I do think he's strong enough to compete at the weight that he's fighting at, but do I think he's the strongest? Nah.

"Do I think he hits harder than Jermell (Charlo)? Nah.

"So come fight night, he's got to prove it. He's got to show us. All the talk is over."

Harrison doesn't believe Tszyu is capable of coping with his relentless left jab.

"I don't think nobody in the world has the ability to do that," he said.

"What he can do is pick his spots to do better and to slow it down, but nobody has the wits and skill to stop it.

"He has the dangers that anybody possesses - just toughness. The grit, the high activity, the pace.

"The same stuff that mostly everybody that comes to fight me possesses when they come to fight me.

"But I'm here. Timothy, oh Timothy, a 24-hour flight. Don't think it's all for nothing brother.

"Get your two-hour workouts in, get your two-hour runs in. Be prepared because I'm not coming over here for nothing."