D.C. United returned home yesterday, disappointed and frustrated by its 4-3 overtime loss to the minor league Charleston Battery in a U.S. Open Cup round-of-16 match Wednesday night in South Carolina.

The outcome made United the third Major League Soccer team to be eliminated from the tournament by a team from the A-League -- the U.S. equivalent of a second division, behind MLS. The tournament features amateur and professional teams from all over the country, but last year, seven of the eight quarterfinalists were from MLS. This season, in addition to United, which was the 1998 MLS runner-up, the defending MLS champion Chicago Fire and the New York/New Jersey MetroStars have been ousted.

"As a coaching staff, these are the games that worry you the most," United Coach Thomas Rongen said. "I think the players are extremely disappointed in the team's performance. And there are some players who are disappointed in their own individual performances."

Said goalkeeper Tom Presthus: "I look at the stat sheet. I made one save and let in four goals. I'm embarrassed with my performance."

United fell behind 2-0 early, but tied the game on a goals in the 28th minute and the 59th minute. A.J. Wood's goal with six minutes remaining in regulation gave D.C. a 3-2 lead. But Charleston scored in the 87th minute, forcing a 30-minute, sudden-death overtime. (The game was not decided by a shootout because the tournament is played under FIFA, not MLS, rules.) The Battery won in the 100th minute on a goal by Ivailo Ilarionov.

"We didn't come out playing well at all," United defender Eddie Pope said. "It was just one of those days where you happen to be flat. That was the day we chose to do it. I don't know if there's any real explanation for it except that we didn't play well."

United was without four starters -- Jeff Agoos, Carlos Llamosa, Ben Olsen and Richie Williams -- who have been playing with the U.S. national team at the Confederations Cup in Mexico. Marco Etcheverry also did not play because of a sore heel. But Presthus refused to use the missing players as an excuse for the team's performance.

"We were missing more players when we played New England [in an MLS game July 25] and we played very well," he said. "We were just careless . . . that's the major factor."

Rongen said he hopes the team will take something from the upset.

"It's a very hard lesson for us to learn, one that we didn't want to learn in this fashion," he said. "The Open Cup was important to us. . . . It cost us dearly, but we're still fighting for the MLS Cup and we're still in the CONCACAF [Champions Cup, the North/Central American and Caribbean club championship tournament]. There's a lot of games to be played, a lot of trophies to be had."

United returns to MLS play Sunday against the Tampa Bay Mutiny.