ESPN Boxing

Junior welterweight titlist Timothy Bradley Jr. and interim titleholder Lamont Peterson will meet Dec. 5 in a mandatory fight, promoter Gary Shaw told ESPN.com Wednesday after winning a purse bid to gain promotional rights to the match.

Shaw, who promotes Bradley, bid $575,000 to beat Peterson promoter Top Rank, which offered $402,500 at a purse bid that took place at the WBO's headquarters in San Juan, Puerto Rico. They were the only two bidders on a fight that had a minimum bid of $150,000.

The fight will be the main event on Showtime's final "Showtime Championship Boxing" of the year, Shaw said.

Also appearing on the card will be junior bantamweight champion Vic Darchinyan (32-2-1, 26 KOs) of Australia, who is returning to 115 pounds after losing a decision to Joseph Agbeko on July 11 in a shot at a 118-pound bantamweight title.

Shaw said he is close to finalizing a match between Darchinyan and Mexico's Tomas Rojas (31-11-1, 22 KOs), who won a vacant interim title on July 18 and is Darchinyan's mandatory challenger.

A third bout could be added to the telecast, Shaw said.

Shaw said he had not decided where the card will take place. He said he is negotiating with three sites, but would not disclose two of them. One of the possible venues is the Agua Caliente Casino Resort Spa in Rancho Mirage, Calif., a few minutes from Bradley's hometown of Palm Springs.

The casino hosted its first boxing event on Aug. 1, when Bradley (24-0, 11 KOs) retained the title in a third-round no-contest against Nate Campbell, a fight that ended prematurely when Campbell was unable to continue following an eye injury caused by an accidental head butt.

However, Shaw may end up taking the fight outside of California because of an arcane WBO rule. Typically, in a purse bid between a titleholder and an interim titleholder, the split of the winning bid is 50-50. However, under the WBO's rules, "if the fight is held in the country of origin, residence or nationality of one of the contenders, the resident contestant shall receive 40 percent and his opponent shall receive 60 percent of the total purse offered."

That means if the bout is held outside of California or Peterson's hometown of Washington, D.C., they each will receive a purse of $287,500.

If the fight is in California, Peterson would receive 60 percent ($345,000) to Bradley's 40 percent ($230,000).

"I have won the purse bid and I have not made a decision where the fight will be held," Shaw said. "I think it's a terrific match. I think Lamont Peterson is a terrific opponent, but I believe that Bradley has fought better competition than Lamont Peterson, so I am not worried about the fight wherever it is held.

"Timmy went to England and won the title against Junior Witter in his home country. He beat Kendall Holt up in Canada. He was going to knock out Campbell in California before the fight was stopped. Wherever it is, I am confident Timmy will come out of the fight as champion and have the opportunity to fight a very, very big fight in 2010."

Had Top Rank won the bid, company boss Bob Arum said he probably would have put it on the Nov. 14 Miguel Cotto-Manny Pacquiao pay-per-view undercard in Las Vegas. But he said he was not disappointed with the outcome of the purse bid.

Arum said he believes the fight will ultimately take place in California, which would give Peterson the lion's share of the money.

"Shaw thought Peterson would only get 50 percent on a purse bid. But he gets 60 percent in California," Arum said. "So Peterson is going to make a windfall. We're lighting candles, we're so happy. I called [Peterson manager, trainer and father figure] Barry Hunter to tell him and they are very happy, like they hit the lottery.

"I think it's a really good fight and I love my guy's chances. I think Lamont Peterson is the real deal."

Peterson (27-0, 13 KOs) claimed the vacant interim belt via seventh-round knockout of France's Willy Blain on April 25 in Puerto Rico.

Dan Rafael is ESPN.com's boxing writer.