The main event of UFC 249 is to be changed as Khabib Nurmagomedov can't leave Russia due to the coronavirus pandemic.
Nurmagomedov was due to face Tony Ferguson at a yet-t0-be determined venue.
But during an Instagram Live chat, the Dagestani fighter conceded that with the Russian borders closed as a result of COVID-19 he would be unable to make the fight.
It's reported that the UFC will carry on with an April 19 date with an alternative opponent for Ferguson.
Should the Nurmagomedov-Ferguson fight be cancelled, it would mark the fifth separate occasion that a meeting of the pair has fallen through.
Nurmagomedov suggests the UFC's dithering over a venue - with options in short supply - led to his inability to take part.
The UAE had been a likely destination.
In his comments translated by RT, he says, "We were training in the AKA without any information regarding the fight, where and how is it going to happen?
"Then the UFC told us that the fight 100% isn't happening in the States. And they said that 99% that it will happen in Emirates, Abu Dhabi.
"After talking to the UFC we decided to fly over to the Emirates a month before the fight. I don't remember the exact date, it was 19th or 20th, I'll have to check.
"But when we landed in Emirates we learned that they are going to close borders. And no one will be able to leave or fly in, with exception for residents.
"So we had to fly back to Russia. Currently I am in Dagestan and I am training and preparing every day. Although I don't know what am I preparing for.
"Because after we came to Russia we also learned that the borders are going to be locked. Same like in the States, same like in Europe, Emirates, everywhere. The whole world is in quarantine right now."
Despite the global lockdown, UFC President Dana White has claimed UFC 249 would see the "baddest card" in MMA history.
Responding to the suggestion UFC 249 will happen without him, Nurmagomedov told his followers, "The UFC told me that this fight 100% isn't happening in the USA, and even if it's not happening in the Emirates it will happen on this side of Atlantic.
"We discussed everything with the UFC. By that time I already spent 5 weeks of hard training in the AKA.
"Now I don't really know what's going on. It's really hard to train and cut your weight when the whole world is locked down and you don't know what you are preparing for. But it's not the first time I face obstacles in my career."