Amir Khan is still hopeful that a fight against Manny Pacquiao can be made for May 20.
Pacquiao's promoter Bob Arum told ESPN on Tuesday that a deal for the eight-weight world champion to face Khan in the United Arab Emirates was "dead."
Arum said the $38m (£31.1m) sought to host the fight in Dubai or Abu Dhabi had failed to materialise from UAE investors.
The veteran promoter has begun considering other opponents for Filipino Pacquiao (59-6-2, 38 KOs), but a source close to Khan (31-4, 19 KOs) told ESPN on Wednesday that the group of businessmen representing the Briton in talks have refused to accept Arum's analysis.
"They are still confident of the fight happening," the source said.
"If it is going to happen, something will happen [be agreed] in the next couple days. There are a group of people with businesses in the U.K. who Amir knows well, and they are handling the negotiations for the Pacquiao fight for him.
"They are still confident that it can materialise. They think the money in the UAE is not an issue. There are people in the UAE keen to have the fight on."
Pacquiao had been due to fight Australian Jeff Horn in Brisbane on April 23, but held an online poll asking who he should fight next, which Khan won overwhelmingly.
Pacquiao and Khan then both announced -- prematurely -- that they would be fighting each other on April 23; it was later moved to May 20. Arum now says it will be November at the earliest if the former sparring partners are to meet in 2017.
Khan has not boxed since being knocked cold by Mexican Canelo Alavarez last May, when the Briton stepped up two weight divisions to challenge for the WBC world middleweight title.
Pacquiao was last in action when he out-pointed Jesse Vargas last November, reclaiming the WBO world welterweight title with his second win after being out-pointed by Floyd Mayweather Jr. in May 2015.