Joseph Parker has submitted his first offer to fight Anthony Joshua, according to his promoter David Higgins.
Negotiations began this week for IBF and WBA 'super' heavyweight champion Anthony Joshua to fight WBC heavyweight Deontay Wilder.
However, the WBO title-holder Parker is still in the mix.
David Higgins responded to Joshua's post on social media on Thursday, exclusively telling Sky Sports: "Joshua is accurate - so I will make an offer. I will underwrite and promote the fight anywhere in the world to give Joshua 60 per cent profit.
"The starting point is 50-50. But as a mark of respect, we would accept a bit less. But we will not accept an insult. Why should we?"
Parker has claimed that dialogue was already underway earlier this week with Joshua's promoter Eddie Hearn.
"We're in talks, 100 per cent," Higgins re-iterated. "Joseph wants the fight but the deal has to be fair and reasonable. If they treat it like a regular voluntary, that devalues it.
"We're not selling our belt. We are going to take Joshua's belts, and we will be paid for our time.
"A proper undisputed world champion has not been done since Lennox Lewis, and if Joshua fought Parker it would a step [in that direction]. So it's not a regular voluntary [defence for Joshua]."
WBC champion Deontay Wilder appears to be in pole position to secure the first world heavyweight title unification fight of 2018 against Joshua. Wilder publicly called out Joshua following his victory Bermane Stiverne.
That outcome wouldn't faze Parker: "We don't care. If Joshua fights Wilder, someone will win and take three belts. Then we will get our shot and it's even bigger," Higgins said.
"We'll take the fight but we're not desperate. If Joshua fights Wilder, we'll fight the winner.
"They will choose between Wilder and Parker. We're here, we're ready."
Parker has "an agreement in principle" to fight Lucas Browne next year. Parker claims he would be content to travel to the UK if a deal can be struck with Joshua.
"For us, March of April [would be suitable] depending on if it's indoors or outdoors," Higgins said. "If I was the promoter I'd look at Wembley or [the Principality Stadium in Cardiff]. The UK is the centre of heavyweight boxing today.
"Eddie Hearn is very straightforward. He wants to make big fights happen. Despite the banter, the guy genuinely wants to unify [the world titles]. We have respect for them."
Earlier this week, negotiations to pit Parker against Wilder have revealed to have quickly broken down.
"Wilder's crew put a figure on the table that wasn't enough," Higgins said at a press conference. "If they put the right money on the table we would go to America and fight Wilder."
Parker added: "I want to fight Joshua. He has got two belts and I want to test his chin and put on a great show.
"Those [other] fights would be good to keep busy, but the ultimate fight is to fight Joshua. He is the preferred option for us."