Four groups are in serious discussions about purchasing the operating rights to D.C. United, club president and general manager Kevin Payne said last night, but a deal worth an estimated $25 million to $30 million does not appear close to completion.

Payne would not name the interested groups, but said one has local ties and another is foreign. According to two sources with knowledge of the situation, the local group continues to be led by Northern Virginia businessman Peter Halpin, who has accompanied Payne to at least two United home matches. One source said the foreign interest comes from the banking industry.

Spanish tenor Placido Domingo, head of Washington Opera and a longtime soccer fan, is interested in purchasing a minority share.

"Several parties are looking at it," Payne said, "and hopefully they're completing their due diligence. They've talked to us, they've talked to the league, they've talked to other MLS investors. Now we're waiting for something to happen."

Under MLS's single-entity structure, each team operator does not own the club but has a financial stake in the league.

U.S. Open Cup

United is expecting to play its first U.S. Open Cup match on Aug. 4, a few weeks later than initially planned, Payne said. MLS clubs received automatic byes to the third round, and barring an upset, United will play the Charleston (S.C.) Battery of the second division A-League.

The Northern Virginia Royals, a United third division affiliate, likely will play Cocoa Beach (Fla.) in an early-round game Thursday at RFK prior to United's game against the Miami Fusion. . . .

Three MLS teams -- San Jose, Kansas City and New York/New Jersey -- are awaiting allocations of foreign marquee players from the league, and it appears MetroStars Coach Bora Milutinovic wants Mexican forward Damian Alvarez, who is under contract with the league but has yet to play this season after appearing for Dallas and New England in previous years. . . . United rookie David Hayes played all 90 minutes at forward in the MLS developmental squad's 2-1 victory at A-League Cincinnati Friday night. . . .

With several defensive injuries to his players, U.S. national team coach Bruce Arena is considering adding Colorado's Marcelo Balboa, a veteran of three World Cups, for next Sunday's game against Argentina at RFK.