Arum said the proposed November 12 second meeting between Pacquiao and Horn, his Australian conqueror, is dead in the water.
Arum is having a hard time talking to his fighter because so many people are in his ear telling him to insist on having the rematch in the Philippines and not Australia because the first fight wound up in a controversial decision going to the hometown guy Horn.
Pacquiao, who also works as a senator, is reportedly having scheduling conflicts with the November 12 fight date.
American contender Jesse Vargas could fill the void left by Manny Pacquiao to fight Jeff Horn for the WBO welterweight title in Brisbane later this year.
Pacquiao was unhappy with the scoring of his shock defeat to Horn in July and struggled against the aggressive Australia's awkward go-forward style. "I am advised Mr. Pacquiao, who is also a Senator of the Philippines, will have other commitments at that time".
Horn's promoter, Duco Events, said the world champion would be "exploring options" to find a replacement.
"On behalf of the Philippines government, he will be part of a delegation that will visit China in the middle of his proposed preparation period for the fight".
But Pacquiao has now changed his mind, pulling out of a rematch of the fight which lost him his World Boxing Organisation welterweight world title to former schoolteacher Horn.
While Lonergan is keen to have Horn's first defence in Brisbane, Arum may be keen to build the fighter's profile in the States. The fight took place before 51,000 fans at an outdoor stadium in Brisbane.
In Brisbane, Queensland Premier Annastacia Palaszczuk said in a statement that Horn looking for another challenger in his title defense.