LAS VEGAS — Manny Pacquiao upped the ante Wednesday in his standoff with Floyd Mayweather Jr. by filing a lawsuit alleging that Mayweather and others defamed him by falsely accusing Pacquiao of using performance-enhancing drugs.

The suit filed in federal court in Las Vegas further complicates efforts to reach an agreement for a proposed March 13 fight between the two boxers. The fight has been stalled by demands by the Mayweather camp that both fighters submit to random blood and urine tests leading up to the bout.

Pacquiao claimed in the suit that he has never tested positive for any performance-enhancing drugs, but that Mayweather, his father and uncle, Oscar De La Hoya and Golden Boy Promotions chief Richard Schaefer embarked on a campaign to make people think he used drugs.

"The truth did not stop Mayweather and the others," the suit contends. "That is because they are motivated by ill will, spite, malice, revenge and envy."

Pacquiao's attorney, Dan Petrocelli, said his client could be out millions of dollars if boxing fans believe he used steroids or human growth hormone to win titles in seven weight classes.

"The damage to his reputation and lost business opportunities could be in the tens of millions of dollars," Petrocelli said.

The suit cites various interviews done by the defendants in which they intimated that Pacquiao's strength and power did not all come naturally. Among the interviews cited was an October radio interview in which Mayweather Jr. allegedly said Pacquiao's physique was different "cause we know the Philippines got the best enhancing drugs."

Schaefer said the suit came as no surprise since Pacquiao had threatened it earlier in the week. He said his attorneys would respond to it, even as talks continue for the fight.

"I'm hearing these talks are being productive," Schaefer said. "Hopefully we will know something in the next couple of days."

Mayweather and Pacquiao had been expected to meet in what promises to be the richest fight ever after they reached agreement over everything from the size of their purses to the make of their gloves for the welterweight megafight. But a demand by Mayweather's camp for both fighters to be subjected to Olympic-style blood testing has stood in the way of a final agreement for the bout.

Talks over the last few days have centered on finding agreement on a date to stop blood testing before the fight, since Pacquiao believes that giving blood may weaken him, at least psychologically.

The lawsuit may not stand in the way of an agreement, but it adds to the increasing rancor between the two camps. In the suit, Pacquiao claims that comments by Mayweather, his father, Floyd Sr., and trainer, Roger Mayweather, were part of a defamation campaign against him.

"Mayweather Jr. and the others set out on a course designed to destroy Pacquiao's career, reputation, honor and legacy and jeopardize his ability to earn the highest levels of compensation," the suit contends.