On Saturday, Horn released a video taunt to Pacquiao saying that while he had less than $38 million on offer, the money being offered to Pacquiao by the Queensland Government, Brisbane City Council and Suncorp Stadium to fight him in Brisbane was "real".
No venue for a Pacquiao-Khan fight has been revealed and last week Pacquiao's promoter Bob Arum said reports he had reached an agreement with Khan were "total and complete bulls***".
On Wednesday Arum said he still had doubts about whether his boxer would see the $38 million being promised.
"Manny seems to believe they will come up with the money," Arum said. "I have some reservations whether it will happen or not."
Horn's promoter Dean Lonergan said he was still hopeful of staging a Pacquiao-Horn world title fight at Suncorp in June or July and remained sceptical that Pacquiao's fight with Khan would materialise.
"I won't believe that Jeff is not Pacquiao's next fight until Bob Arum tells me the deal if officially off," Lonergan said.
"We had already moved on from April 23 in Brisbane because with Manny talking to Amir Khan there was not enough time to get a promotion done in Brisbane.
"We're now hopeful we can put the fight together in June or July. The whole situation is incredibly bizarre.
"It's one thing for two fighters to announce that they have reached an agreement but another thing for the promotion to take place.
"We still don't know the venue for the Amir Khan fight, who is paying the money and who is promoting it.
"Bob Arum is Manny Pacquiao's promoter and I speak with Bob daily. He has zero reason to tell me anything other than what's happening.
"If Pacquiao and Khan can make the deal and they make tens of millions each, then good luck to them but at the moment the fighters are doing all the talking and not the promoters.
"Fighters don't book stadiums, they don't make the global television deals."
On Sunday, Pacquiao tweeted: "Negotiations between team Pacquiao and team Khan have come to terms for the April 23 bout as this is what the fans wanted."
Khan had topped a poll earlier this month after Pacquiao asked his Twitter followers to decide on his next opponent. Khan won with 22,000 votes compared to just 3,000 for Horn.
Khan, who was crushed by Mexican Saul ``Canelo" Alvarez in his last fight in May, tweeted: "My team an I have agreed terms with Manny Pacquiao and his team for a super fight #pacquiaokhan #April23rd".
Pacquiao and Khan trained together under California boxing guru Freddie Roach until 2012.
In 2014 Roach claimed there was no point in Pacquiao fighting Khan.
"Manny frequently put Amir on the floor, knocking him cold four or five times," Roach said.
"There's no point Manny fighting Amir. The reality is that it's no big fight."
