(CNN) -- Nevada boxing officials are trying to end the dope test impasse threatening the Manny Pacquiao-Floyd Mayweather mega-fight, but their demand for immediate urine tests still may not solve the problem.
The Nevada State Athletic Commission said on Monday that Filipino Pacquiao and American Mayweather must submit to the tests within 48 hours or face possible fines or suspension by the commission.
"That at least starts the ball rolling," said Keith Kizer, the commission's executive director told reporters.
But Mayweather's camp issued a statement on Monday indicating Pacquiao's reluctance to undergo blood testing within 30 days before the fight remained a stumbling block.
"Let the record be clear: Manny Pacquiao and his promoter Bob Arum are threatening to walk away from the largest fight in history," a statement from Mayweather and Golden Boy Promotions said.
Arum had given the Mayweather camp a final-offer on Sunday, proposing three blood tests on each of the fighters and none within 30 days of the fight. Pacquiao has said he fears having blood drawn less than 30 days before the fight would weaken him.
Arum said he would open negotiations for a fight with Paul Malignaggi if Mayweather's camp did not agree.
There appeared to be progress later in the day, however, after Mayweather's camp noted that broadcaster HBO's "24/7" program following Pacquiao's preparation for his fight against Ricky Hatton showed Pacquiao having blood drawn 14 days before he knocked out the Englishman.
Mayweather's promoter, Richard Schaefer, said he was told, with that in mind, representatives of Arum's Top Rank would talk on Tuesday to Pacquiao in the Philippines to see if he would agree to a cut-off date for blood testing closer to the fight date than 30 days.
"We were at two days (before the fight), 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."
There is plenty of incentive to get past the problems and get in the ring. The fight, scheduled for March 13 in Las Vegas, could be the biggest moneymaker in boxing history.
Unbeaten Mayweather says the blood tests, which could detect substances not found by urine tests, are vital to ensure a fair fight, although blood tests are not routinely used in boxing.
"It is disappointing for us to see that the benefits of blood testing and the fact that many different substances and procedures can only be detected by blood testing, are still not fully understood by all," the Mayweather camp statement said.
"Their 'take it or leave it' approach, where blood testing would stop 30 days prior to the fight unless the Nevada State Athletic Commission (NSAC) approved differently is another indication that they may not want this fight."
Kizer said he informed both fighters that they must take the urine tests, saying Pacquiao would have to find an accredited agency to conduct his in the Philippines.
"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 fight happening. But with all this talk of drug tests, let's actually do one."