"The preference for all parties is for the fight to be held in Australia, and we are working towards this outcome," said Duco director Dean Lonergan, who met with influential Top Rank boxing supremo Bob Arum this week to broker the deal.
Arum said he wants the fight to take place at an outdoor stadium.
It would be beamed into 159 different countries, including the US, where it would be shown in a primetime Saturday night timeslot on free-to-air TV.
"I would expect 3-4000 Filipinos to fly from the Philippines for this fight down under," Arum said.
"It will be the biggest fight in Australian history but, until the money is secured, we have to keep our options open, including looking at the Middle East and USA."
Horn (16-0-1) is a former schoolteacher who first took up fighting to protect himself from bullies.
He fought at the 2012 Olympic Games in London and has quickly risen through the ranks as a professional, sitting at No.2 in the WBO's welterweight rankings.
Pacquiao, 38, is the WBO champion in that division and has a 59-6-2 record, while also juggling a career as a senator in the Philippines.
Horn - who is a decade younger - has already been installed as a rank outsider by bookmakers but believes he has what it takes to beat Pacquiao.
His trainer, Glenn Rushton, said it would be a "tragedy" if the fight happened anywhere other than Brisbane.
"We really hope the Queensland government and so forth will feel the same way," he said.
"It just makes sense, but also for the future. This can reinvigorate boxing in Australia."
PACQUIAO VS HORN - IN A NUTSHELL
* Fight locked in for Sunday, April 23
* Competitive tender process set to begin for hosting rights
* Brisbane preferred option, but Sydney, Melbourne or Adelaide expected to bid
* Bout could be moved to Middle East or USA if funds can't be raised in Australia.
- AAP
