Amir Khan has accused Floyd Mayweather of taking the easy option in choosing to fight Marcos Maidana on 3 May.
But Britain's ex-world champion still wants to take on boxing's undisputed pound-for-pound number one.
"Floyd probably wants to take the easy route and he's taken Maidana," said the 27-year-old from Bolton.
Khan, who has won 28 and lost three of his 31 career fights, thought the fight with the WBC welterweight world champion was a done deal and says he turned down a match with IBF champion Devon Alexander in December.
"I'm upset about the fight not happening," Khan, 27, told BBC Radio 5 live. "I know there are a lot of fans throughout the world who wanted to see the fight.
"It's a setback for me because it's a fight I've been looking at for the last couple of months.
"I even called off the fight against Devon Alexander which was for the world title last December. I pulled out of that fight because I thought I had the Floyd Mayweather fight 100%.
"Contracts were sent to Floyd and his team. We had signed contracts so I thought back in December it was going to be announced, maybe in January or February, that I was going to fight Floyd Mayweather.
"Then I find out he wanted to do a poll to let his fans pick who he should fight. I won the poll by 57% and then he goes the opposite way and picks Maidana
"Maidana beat [Adrien] Broner but everyone knows it's a fight that Mayweather is going to walk through.
"I beat Maidana in 2010. Speed is what beats him - he is flat-footed."
British welterweight Kell Brook has been suggested as a potential opponent, but Khan said: "He has to up his game a little bit to get that fight.
"In America no-one really knows Kell and the biggest boxing market is in America. In the UK it would be a huge fight but at the moment he is not on my radar."
Maidana has a professional record of 35 victories and three defeats - the last of which was against Devon Alexander in 2012.