Conor McGregor says he is back on the card for UFC 200, but event organisers claim no new talks have taken place.
The 27-year-old had been set for a rematch with Nate Diaz, who beat him in their welterweight fight in March, at the Las Vegas event in July.
After a dispute over promotional duties, UFC president Dana White said organisers were looking for a replacement for the Irishman.
But McGregor said on Sunday: "Happy to announce that I am back on UFC 200."
Writing on social media, he added: "Shout out to Dana White and Lorenzo Fertitta on getting this one done for the fans. Respect."
But US media, including the Los Angeles Times, quoted White as saying: "We haven't talked to Conor or his manager since the press conference. I don't know why he would tweet that."
And McGregor's manager John Kavanagh later added: "I'm 51% optimistic and 49% pessimistic, if you want to know my feelings on it."
McGregor started speculation he was quitting last week when he tweeted: "I have decided to retire young. Thanks for the cheese."
But in a statement two days later, he said: "I am not retired."
White claimed McGregor was withdrawn from the card for refusing to fly to Las Vegas for a news conference and promotional photographs.
In his statement, the fighter claimed he was being asked to do too much promotional work by the UFC and was not able to concentrate on his training.