Bob Arum left the door open a crack for a Manny Pacquiao-Floyd Mayweather Jr. fight on Nov. 13 but it seems very unlikely that Mayweather will walk through.

Arum, Pacquiao’s promoter, announced on a midnight conference call that he will now begin talks with another potential opponent — Antonio Margarito or Miguel Cotto — because Mayweather missed what he called an “exclusivity deadline.”

Mayweather still has time to accept the fight against Pacquiao but the door would be closed the minute Arum reaches a deal with another opponent. Arum said he wants to have an agreement for a Nov. 13 fight in place within 10 days.

Arum didn’t lash out at Mayweather or anyone in his camp, as he did when negotiations for a fight in March fell apart. He speculated that Mayweather has thus far refused to accept the fight because his uncle and longtime trainer, Roger Mayweather, is due in court on assault charges on Aug. 2. Thus, the younger Mayweather would face the prospect of preparing for the biggest fight of his life without his trainer if his uncle is convicted and spends time in jail.

Arum, who negotiated with Mayweather through HBO Sports President Ross Greenburg, doesn’t understand why Mayweather hasn’t been heard from in several weeks but doesn’t place blame on him.

“Obviously people want the Mayweather-Pacquiao fight,” Arum said. “I think the fans are going to be disappointed. They have to realize .. they have to cut Floyd Mayweather some slack. We know his uncle is facing some difficulties in the courts in Nevada. And I can see his reluctance to commit to a big fight with Pacquiao without the services of his uncle.

“If boxing fans begrudge him that, that’s really sad. I really believe people should be understanding.”

Arum said last month that he believed, based on his conversations with Greenburg, that the sides had resolved the sticky issues that stood in the way of the biggest-possible fight in the sport. That included blood testing, the disagreement that scuttled negotiations for the proposed fight in March.

The promoter was asked on the conference call whether he was given any hint as to why Mayweather has thus far failed to commit.

“The answer is no,” he said. “They kept assuring Greenburg, based on what he told me, that Al Haymon [Mayweather’s advisor] told him he was working on it. ÔǪ It just never materialized. I don’t blame Haymon. I think he really tried based on what I got from Greenburg.”

Arum said he set the deadline four months before the fight because he needs time to prepare the promotion and to cope with the unusual complications presented by Pacquiao’s congressional duties in the Philippines.

“The deadline was the end of the exclusivity period,” said Arum, who had promised Greenburg that he would not negotiate with anyone except Mayweather until the deadline passed. “Now I have to go out and secure an opponent for Manny Pacquiao, assuming he won’t fight Floyd. Then we have to mount a campaign, to get in touch with the [satellite TV companies] and get everything in order. Time is going by. Also, we have to start scheduling press conferences.

“ÔǪ I’m dealing with a very unusual situation,” Arum added later in the call. “I’m representing a fighter who is also a congressman. He has legislative duties; he has commitments in the Philippines. We have really short windows to do various aspects of the promotion.”

Arum said he would talk to Pacquiao shortly to determine which of the two primary alternatives to Mayweather he prefers. All three fighters are promoted by Arum.

Margarito is presumed to be the first choice at least in part because Pacquiao has already knocked out Cotto. However, Margarito has issues related to the revocation of his license in California after he was caught with illegal knuckle pads before his fight against Shane Mosley last year.

The Mexican fighter applied for a license in Nevada, apparently with the Pacquiao fight in mind, but the commissioners there tabled his request and told him to apply for reinstatement in California first. However, it looks as if California cannot hear Margarito’s case for several months.

Thus, Arum said that he will ask Nevada to grant Margarito a one-time conditional license for the Pacquiao fight if the Filipino wants to fight Margarito. If Margarito is turned down, Arum said, the fight would be held in Monterrey, Mexico, which apparently has erected a new arena.

The Cotto fight would take place either in Las Vegas or Cowboys Stadium, the site of Pacquiao’s victory over Joshua Clottey in March.

The appeal of a rematch with Cotto, a junior middleweight titleholder, is the opportunity for Pacquiao to win a belt in a record eighth weight division.

“And Miguel will have in his corner Emanuel Steward, one of the great cornermen of our time,” Arum said. “That certainly would give Cotto more ammunition than he had going into the fight the last time.”

Meanwhile, those who want to see Pacquaio-Mayweather will hope that it still somehow happens. Arum is among them.

“[Pacquiao-Mayweather] is dead when we conclude a deal with an opponent for Manny’s fight in November,” he said. “Then we’re contractually bound to do that fight. And we would look hopefully do a fight with Floyd next year. In the interim … if Floyd suddenly emerged and said yes, he wants to do fight, there would be nothing opposed to getting together and doing a fight.”

Floyd?