Since departing as D.C. United's coach last winter, Bruce Arena has been a frequent visitor to United Park as an observer and friend. But yesterday he returned to Herndon on official business as coach of the U.S. men's national team, which will train at the facility all week in preparation for Sunday's friendly match against Argentina at RFK Stadium.

"Coming back here, there was a big tear in my eye during training," Arena said without the slightest bit of seriousness. "Actually, I haven't exactly left."

After three seasons and two Major League Soccer championships, Arena still is part of the United family. There was no better illustration of that than yesterday morning.

After the national team completed the first of two 90-minute workouts, the U.S. players (including three United starters who were selected) headed toward the locker room as the rest of the United players emerged for their daily session with Coach Thomas Rongen.

Arena greeted several of them, teasing D.C. forward A.J. Wood about smashing his car windshield with his own wayward shot in practice last week and trying some of his indecipherable half-Spanish, half-English lines on United's Latin American players. It was just like old times.

And like the previous few years, Arena is here planning to build a winner. He has summoned 21 players, ranging in age from 17 to 32, from four leagues overseas and six MLS teams, to face two-time World Cup champion Argentina.

Under Arena, the United States is 3-1-2, highlighted by a 3-0 upset of Germany in Jacksonville, Fla., in February. Sunday's match is a difficult primer for this summer's FIFA Confederations Cup in Mexico, when the Americans will play Germany and Brazil in the first round.

"We're far from being a good national team," Arena said. "All these opportunities are important. As long as we make progress, get a good work ethic and a good team concept going, I think we'll be okay. . . . Right now, we're just starting from scratch again. We need to get familiar with each other and understand what we're trying to do -- and that takes time."

United forward Roy Lassiter, midfielder Richie Williams and defender Jeff Agoos will practice exclusively with the national team this week. Defender Carlos Llamosa, who's recovering from a sprained knee and ankle, likely will join them today after sitting out yesterday's workouts.

Rongen said Llamosa will not play for United Thursday night against the Miami Fusion at RFK, so he doesn't aggravate the injuries. As for the availability of the others, Arena and Rongen will discuss it today or Wednesday. "I expect a compromise will happen," Rongen said.

Rongen said he expects Arena to let him use players who aren't projected to start against Argentina (Williams and perhaps Lassiter), leaving only Agoos's status unresolved. Miami likely will have the services of defender Leo Cullen, who was a late addition to the U.S. squad.

With the playing roster limited to 18, one or two other U.S. players may be released to their MLS clubs in time for weekend league games.

"We don't want to badly impact D.C. United or MLS," Arena said. "The teams we can help, we'll help."

Arena added one more player to the U.S. roster yesterday: New England defender Ted Chronopoulos, who has made one international appearance.

Soccer Notes: Argentina plays Mexico Wednesday in Chicago before arriving in the Washington area Thursday. It will train at RFK Stadium and George Mason University. . . . Arena's assistants are University of Virginia Coach George Gelnovatch and American University Coach Bob Jenkins. . . . Ticket sales have surpassed 24,000. . . . With a possible player shortage Thursday, Rongen will have rookie forward David Hayes available. Hayes has been impressive for MLS's developmental squad, recording a team-high four goals.