Mahmoud Charr's WBA heavyweight title defence has been thrown into serious doubt after he did not travel to America for Friday's fight against Trevor Bryan.
The Germany-based Syrian was due to make his first defence of the WBA 'regular' belt, over three years since claiming the title, but could not obtain a correct visa in time for him to board a plane to Miami on Wednesday morning.
Charr had said on Tuesday that he needed signed paperwork from Bryan's promoter Don King to allow him to travel for the fight.
He has since told Sky Sports: "I did not fly. When I was in the embassy, I have B1, B2 visa, but they have told me if I fly to Miami, I have to stay two weeks in quarantine, a bubble.
"We can only give you B1 and B2, but if you fly with this, you have to stay two weeks in quarantine, you cannot fight."
Carl Lewis, attorney for Don King Productions, clarified Charr's visa status, telling Boxingscene.com: "The issue was that Charr did not have the right kind of visa allowing him to fight in the United States.
"The visa he has obtained allows him to travel to the US, but his P1 visa application is still pending. If he was granted a P1 work visa, he could fight. If not, he can't fight."
The WBA champion's promotional team had dismissed any suggestion that the WBA could take action against Charr, if the fight does not go ahead.
"The WBA know us as a very professional promotion. So they know we fulfil everything with the best professionalism," promoter Erol Ceylan had told Sky Sports earlier in the week.
"There is no reason to strip Charr for failure of other people. They have confirmed that to me personally several times."
Anthony Joshua holds the widely recognised WBA 'super' belt, along with the WBO and IBF titles that were also at stake in his ninth-round knockout win over Kubrat Pulev in December.
Charr had insisted that the winner of his fight with Bryan, who is WBA interim champion, will secure a guaranteed fight against Joshua.
"This is the mandatory fight for Joshua," said Charr.
"I hope the fight will happen. I'm the first heavyweight champion from the Middle East.
"I know when I beat Trevor Bryan, (Joshua's promoter) Eddie Hearn can make the fight in Qatar, or Saudi Arabia, because I'm the first Arabic heavyweight from this area.
"That will be a big, big show for everyone in the world."