Horn's camp want the bout over 10 rounds and are adamant a rematch clause must be included in the 14-page contract promoter Dean Lonergan handed to Tszyu's promoter Matt Rose.

But Tszyu's camp want the fight on 12 rounds without a rematch clause in the hope they can move on to a world title shot in the immediate aftermath.

Lonergan says he struggles to see the fight going ahead in April if Tszyu's camp don't agree to the terms within the next seven days.

"They want the fight over 12 rounds, we want it over 10 and we're not moving," Lonergan said.

"There will be no fight without a rematch clause and we're adamant on that. Matt got very heated in the debate. He said 'we're not going to have that, if we win this we're onto a world title'.

"I personally think they're kidding themselves because I know the landscape backwards. A world title at the back of this is not a possibility.

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"It might be for Jeff Horn, but not for Tim Tszyu. Jeff Horn has got a much bigger name than Tim Tszyu.

"Right now, the fight absolutely hangs in the balance and they're very aggressive on these points which I find fascinating. It got very heated.

"We're probably going to give ourselves seven days to do it. If they can't concede to it, I struggle to see it going ahead."

The fight is slated for a Wednesday night in April to avoid clashes with major football codes while a venue is yet to be determined.

Lonergan says the switch to a midweek date simply made sense given "you're probably losing one to two million" viewers on a Thursday, Friday or Saturday due to AFL and NRL games.

Tszyu's camp has agreed to a 60-40 split in Horn's favour with Lonergan adding even that was a generous offer given the latter's resume.

The former welterweight world champion shot to fame with a win over Manny Pacquiao before taking on one of the sport's pound for pound kings in Terence Crawford under the bright lights of Las Vegas.

More recently it was Horn's remarkable win over Michael Zerafa in a rematch that drew headlines across the nation in one of Australian boxing's all-time classics.

Lonergan says the ball is now in Tszyu and Rose's court with Horn's team refusing to budge. A rematch would also be contested over 10 rounds.

"Here you get to fight a guy who is absolutely world class," Lonergan said of Horn.

"He's beaten Pacquiao, been in with Crawford, come back from Zerafa, he's won a Don. He's done everything in the sport.

"Do you want to step up to the big time boys?"