Amir Khan's scheduled fight against Manny Pacquiao has been called off, according to the Filipino's promoter Bob Arum.
The two fighters had announced the "super fight" on Twitter at the end of February, with only the location to be determined.
A venue in the United Arab Emirates was expected to be confirmed but Arum says the 23 April showdown is now "dead".
Speaking to ESPN, Arum said: "[Pacquiao's adviser] Michael [Koncz] is on his way back to meet with Manny but it's kaddish for the UAE deal. It's dead.
"I'm talking to him about another proposal for another fight, not Khan. Khan won't be Manny's next opponent."
Pacquiao, 38, who currently holds the WBO welterweight title, tweeted last month: "Negotiations between team Pacquiao and team Khan have come to terms for the 23 April bout as this is what the fans wanted."
Khan had posted in February: "My team an I have agreed terms with Manny Pacquiao and his team for a super fight #pacquiaokhan #April23rd."
Pacquiao continues to be trained by Freddie Roach but Khan left the American in September 2012 and is now under the tutelage of Virgil Hunter.
Khan's last fight in May 2016 was at 155lbs, when he challenged Mexico's Saul Alvarez for the WBC middleweight title but lost in six rounds.
He has also long spoken of fighting in the UAE, where he has a southern Asian fanbase, and of his desire to test himself against either Pacquiao or Floyd Mayweather, two of the finest fighters of the modern era.
The 30-year-old previously said: "When I sparred with Manny he was dangerous. They were hard rounds and I knew then that one day I would fight him. I have been ready for a long time."