MANILA, Philippines – Controversial boxer Floyd Mayweather Jr. threw verbal jabs yet again at Manny Pacquiao by saying he'll only fight "all-natural" boxers.

"I really feel bad for the fans that have been waiting for the Pacquiao fight for so long," the undefeated boxer told Fighthype.com.

"It's just, if I fight a fighter, I want to make sure that fighter is 100% all-pure and all-natural."

Mayweather, who faces Victor Ortiz in September, said refuses to stake his 41-0 record against Pacquiao because he claimed that the Filipino boxing superstar refused to take random blood testing.

"He just doesn't want to take these same test[s]. I work too hard to take a chance of losing to a fighter that's cheating," he said.

But Mayweather, who still has a pending defamation suit from Pacquiao, was careful from accusing Pacquiao of performance enhancement drug (PED) use.

"I'm not saying that Manny Pacquiao is cheating," he said.

"That just goes for any fighter. Any fighter that's getting in the ring with Floyd Mayweather must take the random blood and urine tests."

Mayweather, also known as "Pretty Boy Floyd," apparently failed to hear Pacquiao's willingness to undergo the tests.

"Pumayag naman ako pero hindi 'yung talagang maraming dugo na kukunin. Kung anong dugo ang kelangan sa drug test, ganoon lang karami. Fourteen days [before the fight]," Pacquiao earlier told ABS-CBN News' Dyan Castillejo.

(I relented to his demand as long as they take just enough blood needed for the test… Fourteen days before the fight.)

Negotiations broke down between the camps of Pacquiao and Mayweather in 2010 when the American boxer demanded an Olympic-style drug testing.

Pacquiao later relented and agreed to drug testing provided that he will be given a 14-day cut off.

Mayweather, however, repeatedly declined to fight Pacquiao despite getting offers as high as $65 million.

