LAS VEGAS — The head of the Nevada boxing commission ordered Manny Pacquiao and Floyd Mayweather Jr. to submit to urine tests today as a way of trying to break the impasse that has threatened to derail their proposed March 13 megafight.

Pacquiao and Mayweather must submit to the tests within 48 hours or face possible fines or suspension by the Nevada Athletic commission.

"That at least starts the ball rolling," said Keith Kizer, the commission's executive director.

Indeed, the two sides signaled late in the day that there could be room for a compromise after Mayweather's representatives said there was footage on HBO's "24/7" program that showed Pacquiao having blood taken 14 days before his knockout win over Ricky Hatton.

Mayweather's promoter, Richard Schaefer, said he was told that Top Rank representatives would be talking early Tuesday to Pacquiao in the Philippines to see what cutoff date he would agree to on blood testing. Schaefer said there was a possibility the two sides could compromise somewhere between Mayweather's demand for testing up until the weigh-in and the 14 days Pacquiao had blood taken prior to the Hatton fight.

"We were at two days and I assume Pacquiao is at 14 days," Schaefer said. "Let's see if somehow there can be a compromise found that maintains the integrity of the tests. If that can be done in a manner acceptable to Pacquiao, I will take it to Mayweather's team."

The urine tests, which were ordered by commission chairman Pat Lundvall, fall under an out-of-competition testing regulation which went into effect last year and allows state boxing authorities to order boxers to comply. Kizer said about 30 of the tests have been ordered in the last 18 months.

The commission's demand comes a day after Pacquiao promoter Bob Arum said he would not budge off a proposal to do just three blood tests on the two fighters — and none within 30 days of the fight. Arum, who had suggested the NAC decide next month who will prevail in the dispute, said he planned to begin negotiating a fight with Paul Malignaggi if Mayweather's camp didn't agree to the terms.

But Mayweather's manager, Leonard Ellerbe, said Monday there would be no fight on Arum's terms, and charged the promoter with trying to shift the blame for the fight not happening from Pacquiao's side to Mayweather.

"If he's unwilling to do random blood and urine it's a nonstarter," Ellerbe told The Associated Press. "He knows that. If they want to walk away from the richest fight in the history of the sport, that's their decision."

Kizer said the urine tests could play a part in breaking the impasse, though Mayweather's camp has said blood tests are necessary to find performance-enhancing drugs that may not be detected by urine tests. Mayweather backed off earlier on a demand for the tests to be conducted by the U.S. Anti-Doping Agency but has insisted all along that they be done randomly and include blood tests within 30 days before the fight.

Ellerbe said his fighter had already made many concessions to get the fight, including the financial split, the penalty for coming in at more than 147 pounds, and the gloves to be used. He said there would be no further concession to meet Arum's terms.

"There's no way," Ellerbe said. "The ball is in their court. But you have to ask yourself why they aren't willing to make sure both fighters are clean to ensure that the biggest fight ever can take place."

Kizer said he informed both fighters that they must take the urine tests, saying Pacquiao would have to find an accredited agency to do his in the Philippines. The state of Nevada is paying for the tests, which cost about $150.

"We're always hopeful that when we do drug testing it comes back negative," Kizer said. "I don't know if this will help the chances of the fight happening. But with all this talk of drug tests, let's actually do one."