Brian Viloria-Omar Nino reset for May

Flyweight titlist Brian Viloria wants revenge on Omar Nino, but he will have to wait a bit longer for the opportunity than he had planned.

Winless in two previous fights against Mexico's Nino, Viloria, a Filipino-American from Hawaii, was due to face him March 31 at Ynares Sports Arena in Pasig City in the Philippines.

However, the fight was postponed a couple of weeks ago and rescheduled on Monday to take place at the same venue on May 12 (Integrated Sports PPV, 9 p.m. ET, $29.95).

"I've been through these changes before," Viloria told ESPN.com. "I've just got to continue with the training and keep grinding."

The reason for the delay is an odd one, even by boxing's often bizarre standards.

There is no injury, no arena issue or television distribution problem. Instead, the fight was postponed because Nino owed an unpaid fine of $11,250 to the Nevada State Athletic Commission dating to his second fight with Viloria in 2006.

They met twice in 2006 in Las Vegas. Viloria (30-3, 17 KOs) suffered his first career defeat and lost his junior flyweight title to Nino in the first meeting. Three months later they fought to a draw in a rematch, but the decision was later changed to a no-contest because Nino (31-4-2, 13 KOs) tested positive for a banned substance after the fight.

Nino was suspended and fined by the Nevada commission following the positive test, but he has still has not paid all of the fine.

According to Nevada commission executive director Keith Kizer, the commission has tried to collect for years. Kizer said he tried to get the WBC to refuse to sanction various Nino bouts until the fine was paid, but the sanctioning organization would not intervene.

After Nino's suspension, he continued to fight in Mexico and also was permitted to fight in various WBC title bouts, including winning (and then losing) its junior flyweight belt in 2010.

After Nino came to terms to challenge Viloria, who will be defending his WBO flyweight title for the second time, Nevada alerted the sanctioning body about the overdue fine. Kizer said the WBO said it would refuse to sanction the bout until it was paid, which led to the postponement.

Kizer told ESPN.com that the Nevada commission still has not received the fine money, but he expects it will before the fight.

"I continue to wait patiently. I expected the money already," Kizer said. "I don't know what the holdup is. Just pay the money. (Nino) fought for the WBC several times and I tried to collect but they kept saying, 'There's nothing we can do.' But with the WBO, it was no problem. They said right away that they would not sanction the fight until he paid and the Filipino commission was also helpful, saying they would do what they can."

Rather than find a new opponent for Viloria to fight on March 31, he agreed to postpone the bout to allow Nino time to sort out the issue with the fine.

"We had a choice of finding a last-minute substitute that would get cleared by the WBO, but there wasn't anybody that made sense," said Gary Gittelsohn, Viloria's manager. "The story line between Brian and Nino was compelling and Brian wants to finish unfinished business with this guy and he agreed to a postponement."

Viloria is just anxious to get Nino back in the ring.

"I'm really hungry to correct my past mistakes with my (upcoming) win over Nino," said Viloria, a 2000 U.S. Olympian and former two-time junior flyweight titlist. "I can't wait and its been my fuel and inspiration in training camp."