Floyd Mayweather Jr's planned bout with Manny Pacquiao is off because of a blood-testing dispute, according to Pacquiao's promoter Bob Arum.
"As far as I'm concerned, the fight is off," said Arum, referring to the scheduled 13 March welterweight bout.
The American's camp were told by Pacquiao's people that the Filipino would not agree to blood-testing in the 30 days prior to the fight.
The welterweight super-fight was expected to be the richest of all time.
Arum accused Mayweather's camp of raising the issue not because they were worried about Pacquiao taking performance-enhancing substances, but because Mayweather never wanted to fight in the first place.
Arum said Pacquiao would agree to testing by the same agencies that test pro American Football and baseball players, but not for random tests by the US Anti-Doping Agency.
Pacquiao's trainer Freddie Roach added: "The sanctioning bodies and the state commissions run the boxing world, not Floyd Mayweather.
"Who is this guy to tell us that we have to have blood tests, or urine tests, or any tests? He's just looking for a way out of the fight."
Mayweather associate Richard Schaefer said: "He, Pacquiao, would only agree to have blood drawn before the kick-off press conference and after the fight.
"It is unfortunate to hear this from Manny Pacquiao's representatives, particularly since both parties had worked out all other issues related to this fight."
Unbeaten Mayweather's management want both men - regarded as the two best pound-for-pound fighters in the world - to submit to blood-testing prior to the bout, to ensure both men are clean.
Schaefer, who is chief executive of Golden Boy Promotions, added: "Todd [DuBoef, president of Pacquiao's promoters Top Rank] told me that Pacquiao has difficulty with taking blood and doesn't want to do it so close to the fight."
Prior to Arum's announcement, the 32-year-old Mayweather had urged Pacquiao to agree to the blood-testing.
"I understand Pacquiao not liking having his blood taken, because frankly I don't know anyone who really does," said Mayweather.
"But in a fight of this magnitude, I think it is our responsibility to subject ourselves to sportsmanship at the highest level."
But Roach countered: "We have passed every test ever given to us. We go by the commission rules, since when does the fighter make up the rules?
"When Manny gives blood it takes him three or four days to recover from it. I am not going to have my fighter going into a fight feeling weak and not sure of himself.
"Mayweather is scared, and he's just afraid that he's going to get his ass kicked."
The fight had been expected to be held at the MGM Grand Garden Arena in Las Vegas.
The Staples Center in Los Angeles, home of the NBA's Lakers was also touted as a possible venue and representatives of Cowboys Stadium in Dallas were also said to be interested in hosting arguably the biggest fight since the turn of the century.
Pacquiao, 31, became a five-weight world champion following his WBO welterweight title win over Miguel Cotto in November, while Las Vegas-based Mayweather returned from a 21-month retirement to beat Mexican Juan Manuel Marquez in September.
Arum added that Pacquiao still plans to fight on 13 March and will now look for another opponent.
BBC Sport - Floyd Mayweather's fight with Manny Pacquiao 'is off'
"As far as I'm concerned, the fight is off," said Arum, referring to the scheduled 13 March welterweight bout.
The American's camp were told by Pacquiao's people that the Filipino would not agree to blood-testing in the 30 days prior to the fight.
The welterweight super-fight was expected to be the richest of all time.
Arum accused Mayweather's camp of raising the issue not because they were worried about Pacquiao taking performance-enhancing substances, but because Mayweather never wanted to fight in the first place.
Arum said Pacquiao would agree to testing by the same agencies that test pro American Football and baseball players, but not for random tests by the US Anti-Doping Agency.
Pacquiao's trainer Freddie Roach added: "The sanctioning bodies and the state commissions run the boxing world, not Floyd Mayweather.
"Who is this guy to tell us that we have to have blood tests, or urine tests, or any tests? He's just looking for a way out of the fight."
Mayweather associate Richard Schaefer said: "He, Pacquiao, would only agree to have blood drawn before the kick-off press conference and after the fight.
"It is unfortunate to hear this from Manny Pacquiao's representatives, particularly since both parties had worked out all other issues related to this fight."
Unbeaten Mayweather's management want both men - regarded as the two best pound-for-pound fighters in the world - to submit to blood-testing prior to the bout, to ensure both men are clean.
Schaefer, who is chief executive of Golden Boy Promotions, added: "Todd [DuBoef, president of Pacquiao's promoters Top Rank] told me that Pacquiao has difficulty with taking blood and doesn't want to do it so close to the fight."
Prior to Arum's announcement, the 32-year-old Mayweather had urged Pacquiao to agree to the blood-testing.
"I understand Pacquiao not liking having his blood taken, because frankly I don't know anyone who really does," said Mayweather.
"But in a fight of this magnitude, I think it is our responsibility to subject ourselves to sportsmanship at the highest level."
But Roach countered: "We have passed every test ever given to us. We go by the commission rules, since when does the fighter make up the rules?
"When Manny gives blood it takes him three or four days to recover from it. I am not going to have my fighter going into a fight feeling weak and not sure of himself.
"Mayweather is scared, and he's just afraid that he's going to get his ass kicked."
The fight had been expected to be held at the MGM Grand Garden Arena in Las Vegas.
The Staples Center in Los Angeles, home of the NBA's Lakers was also touted as a possible venue and representatives of Cowboys Stadium in Dallas were also said to be interested in hosting arguably the biggest fight since the turn of the century.
Pacquiao, 31, became a five-weight world champion following his WBO welterweight title win over Miguel Cotto in November, while Las Vegas-based Mayweather returned from a 21-month retirement to beat Mexican Juan Manuel Marquez in September.
Arum added that Pacquiao still plans to fight on 13 March and will now look for another opponent.
BBC Sport - Floyd Mayweather's fight with Manny Pacquiao 'is off'
