The much-anticipated showdown between Manny Pacquiao and Floyd Mayweather, tentatively scheduled for March 13 at the MGM Grand in Las Vegas, has collapsed, Top Rank promoter Bob Arum told ESPN.com on Wednesday night.

"The fight's off," Arum, who promotes Pacquiao, said from Las Vegas.

The fight died after a last-ditch attempt at mediation between Top Rank and Golden Boy, which represents Mayweather, failed in an effort to determine the drug-testing protocol.

Pacquiao had agreed to move off his hard-line stance of refusing a blood test inside 30 days before the fight, but Mayweather wouldn't budge off his desire for random testing all the way until the fight, Arum said. Nor would Mayweather agree to a public apology for remarks he made accusing Pacquiao of using performance-enhancing drugs, Arum said.

"I am very disappointed that we could not make this fight for the fans and I am angered because of the false accusations from Golden Boy and the Mayweather camp that I used some type of drugs, and that is why I have instructed our American lawyers to proceed with the lawsuit to clear my name," Pacquiao said in a statement.

Arum said Pacquiao would move on and likely fight junior middleweight titlist Yuri Foreman on March 13 or March 20.

The fight was to have been on HBO PPV, a sure blockbuster many believed would break the all-time pay-per-view record of 2.44 million buys set by Mayweather's 2007 fight with Oscar De La Hoya, who owns Golden Boy Promotions. But Arum said he had informed HBO PPV boss Mark Taffet that the fight was off.

Had the fight done the monster numbers organizers expected, it would have likely generated in the neighborhood of $200 million with the fighters receiving roughly $40 million apiece.

Richard Schaefer, the CEO of Golden Boy and the point person for the company on the negotiations, did not return multiple messages.

The sides had negotiated every point of the deal except for the drug testing procedures. The fighters agreed to unlimited random urine testing, but Mayweather insisted on random blood testing as well, even though the Nevada State Athletic Commission, which would regulate the fight, requires only urine testing.

Pacquiao (50-3-2, 38 KOs) didn't want any blood testing but had agreed to take three blood tests: one during the week of the kickoff news conference, which would have taken place next week; one random test to be conducted no later than 30 days before the fight; and a final test in his dressing room after the fight. Mayweather (40-0, 25 KOs) would have been subject to the same testing procedures.

When they could not come to an agreement on the drug testing, they enlisted the aid of a mediator, retired judge Daniel Weinstein, who successfully mediated a series of disputes between Top Rank and Golden Boy, which represents Mayweather, in June of 2007. At the center of the problem was ownership of the promotional rights to Pacquiao, who had signed contracts with both companies before eventually pledging his loyalty to Top Rank. Under the settlement, Top Rank got Pacquiao's contract with Golden Boy retaining a small percentage.

With lawyers at their side, Top Rank's Arum, company president Todd duBoef, Golden Boy's Schaefer and De La Hoya, along with Mayweather adviser Al Haymon, spent nine hours in mediation on Tuesday in Santa Monica, Calif.

The sides struck a deal during the marathon session Tuesday, but it was contingent on getting the fighters to sign off, Arum said.

On Wednesday, they were back in their offices -- Golden Boy in Los Angeles and Top Rank in Las Vegas -- and worked the phones with their clients while still under Weinstein's gag order not to talk to the media.

Arum said Pacquiao agreed to ease his demands on the drug testing window but Mayweather wouldn't.

Arum said Pacquiao agreed to shorten the window for a blood test to 24 days before the fight. In order to receive a Nevada boxing license, Pacquiao took the standard annual blood test 24 days before his May 2009 fight with Ricky Hatton.

"Manny accepted what was on the table and Mayweather rejected it," Arum said. "Haymon and Schaefer tried to convince Floyd all [Tuesday night] and [Wednesday] and he wouldn't agree to it. He didn't want the fight. He never wanted the fight. I always knew the fight wouldn't happen."

The drug testing became a major issue when Floyd Mayweather Sr., the father of the fighter, made several public remarks accusing Pacquiao of using performance-enhancing drugs without a shred of proof. Mayweather Jr. later made similar remarks about Pacquiao using PEDs, even though Pacquiao denies it and has never failed a drug test.

"When the fight was offered, Manny accepted it with no hesitation," Pacquiao adviser Michael Koncz told ESPN.com from the Philippines, where he was with Pacquiao. "We're not surprised. We saw this coming once they started this drug bull----. It was a way for them to get out of the fight. I don't think Mayweather expected Manny to accept the challenge so quickly."

The accusations led Pacquiao to file a defamation lawsuit last week in Nevada U.S. District Court against Mayweather Jr., Schaefer, Golden Boy president De La Hoya, Floyd Mayweather Sr., Roger Mayweather and Mayweather Promotions.

"The guys who should be most disappointed in the fight being off are Schaefer and De La Hoya because they went along with this guy [Mayweather] and ended up with gatz and a big lawsuit," Arum said.

Said Koncz: "We agreed to move the drug testing to 24 days under the supervision of the Nevada commission and Mayweather still wouldn't budge. So now what we've done is give up maybe $40 million to take a stand for Manny's principles. We will proceed with the lawsuit in an effort to clear his name and tarnished image. Even if they make a public apology it's not enough. Now they'll have to prove to a judge that Manny is on drugs, which they won't be able to do because he's not. Manny is pissed off because he feels Floyd is a chicken and because he tarnished his reputation. This is about principle. We have nothing to hide."

Golden Boy also risks losing its share in Pacquiao's contract, Arum said.

"There's an arbitration which calls for them to lose any percentage of Manny's promotional contract, something we asked for and had postponed, but now it will go forward," Arum said. "We did that two weeks ago before Manny filed his lawsuit. It's binding arbitration. Our request was for Golden Boy to forfeit its interest in Pacquiao's contract based on the fact that they had demeaned Pacquiao with their remarks [alleging he used PEDs] and that it violated the [2007] agreement between Pacquiao, Top Rank and Golden Boy."

Arum now plans on moving forward with Pacquiao facing Foreman, who won his 154-pound title on the Nov. 14 undercard of Pacquiao's 12th-round knockout of Miguel Cotto to win a welterweight belt. Pacquiao would move up in weight to try to win a title in his eighth division. Pacquiao already holds the record, having won titles in seven divisions.

Mayweather could also still fight on another date in March, potentially against former junior welterweight titlist Paulie Malignaggi.

"We're going to talk to the MGM because they're out of a fight," Arum said.

Arum added that the fight could also wind up at the Thomas & Mack Center in Las Vegas or perhaps in Dallas, where Cowboys owner Jerry Jones made a strong pitch to bring Pacquiao-Mayweather to his new stadium.

Dan Rafael covers boxing for ESPN.com.