Dean Lonergan, promoter for former WBO welterweight champion Jeff Horn, is working hard to get over the finish line for an Australian mega-bout with undefeated rising star Tim Tszyu.

Tszyu, the son of former undisputed champion and Hall of Famer Kostya Tszyu, has been calling for a fight with Horn since last year.

Horn bounced back in force back in December, when he dropped Michael Zerafa twice to secure a majority decision in their drama-filled rematch.

The discussions for a Horn vs. Tszyu encounter have taken a step further after Tszyu's promoter, Matt Rose, reportedly accepted a 60-40 split to do the fight.

The date of April 18 is the target for the contest.

Lonergan cautions that a split agreement is just one piece of the puzzle to get a deal done.

"They might have accepted the 60-40, but that doesn't mean anything. The reason I say it doesn't mean anything is there is a whole lot of detail to work out," Lonergan said to the Canberra Times.

"First and foremost, you have to get stuff in there about rematch clauses and how they would work, that was a big bone of contention with Michael Zerafa. Are they prepared to go where we tell them to go? I don't know, all I've seen and heard is they will accept the 60-40 but that's just the start.

"There's a long way to go. I haven't had an in-depth discussion with Matty Rose yet. Until Matt and I nail all the details and get a signed agreement, as far as I'm concerned there is nothing in place. We've got a long way to go yet, if they have agreed to the 60-40 which they're saying in the media, which I don't think they will back away from, there's a whole lot of detail to go through yet. This is far from done."