Wales' former super-featherweight world champion Joe Cordina, 34, had been due to take on WBO lightweight champ Abdullah Mason in Cleveland on Saturday, 4 July.
But Cordina says the United States embassy in London surprisingly turned down his visa application.
In a social media post Cordina stated: "I was due to fly to the United States this week. A couple of days back I went to the US embassy in London and they basically denied me a visa.
"I tried to explain certain things, and had all the paperwork to back it up, and they wasn't having it.
"They just sort of basically told me you ain't getting in, so it's on my hands.
"Absolutely gutted, because it's my chance to become a three-time two-weight world champion, plus fight for a world title in America, which was a goal of mine."
The Commonwealth Games bronze medallist Cordina added he "feels bad" for his opponent Mason and denied suggestions he has suffered an injury.
"I've seen a load of things saying injuries, and this, and there's no injuries. I've had a great camp," said Cardiff's Cordina.
The Cordina fight was set to be Mason's first defence of the belt he won in an epic encounter with Briton Sam Noakes in November 2025.
'The Welsh Wizard' had been hoping to become a two-weight world champion.
He lost his IBF 130lb world title in May 2024, a shock defeat by Irishman Anthony Cacace, the only loss in his 19-fight professional career.
He has since beaten Jaret Gonzalez Quiroz to claim the vacant WBO global lightweight title before dominating Gabriel Flores Jr for the WBO International belt in California on the way to a unanimous victory on points in December 2025.
Cordina won British and Commonwealth titles at lightweight earlier in his career, having been a decorated amateur boxer who fought at an Olympics and in the same Team GB programme as his friend Anthony Joshua.
After turning professional in 2017 he became Wales' 13th world champion boxer when he beat Kenichi Ogawa to claim the IBF super-featherweight title in June 2022.
Cordina was stripped of the title when he was unable to defend it within a 90-day window after suffering a broken hand, but won it back with a hard-fought split-decision win over Shavkatdzhon Rakhimov in April 2023.
He was a strong favourite to retain his belt in Riyadh in May 2024, but the referee stopped the fight in the eighth round of a bout dominated by Belfast's Cacace.
Cordina was scheduled to make a comeback against Shakur Stevenson in October 2024, but the WBC lightweight champion pulled out with a hand injury.
Returning from a 14-month lay-off in July 2025 he beat Gonzalez Quiroz with a hard-fought points decision at Manchester's AO Arena, needing to dig deep against the quick-handed and spirited Mexican.
Trained by Tony Simms, Cordina was given a scare by Flores Jr in a fight billed as a final eliminator for the WBO lightweight world title. The Welshman was docked a point in the sixth round in Stockton for rabbit punching and saw his knees buckled by an uppercut in round seven.
However, Cordina went on to win his first fight in America 117-110 115-112 114-113, establishing himself as Mason's number one contender.