D.C. United, seeking experienced players to solidify its roster following two recent trades, is negotiating to acquire Bulgarian defender Galin Ivanov and has taken an interest in U.S. World Cup veteran Earnie Stewart.

Ivanov, 27, starts for the top club in Bulgaria, CSKA Sofia, and has played for his national team. He is primarily a central defender but also can fill other roles.

United Coach Ray Hudson said he is "very optimistic" a deal can be reached to acquire "a Bulgarian defender," but declined to reveal the player's identity. However, The Post has learned that United has targeted Ivanov and that contract negotiations are progressing well, with a deal possible within a month.

Ivanov's agent, former Bulgarian player Latchezar Tanev, did not respond to an e-mail message seeking comment. Major League Soccer officials in New York, who oversee player acquisitions, declined to comment.

Stewart, who will turn 34 in March, has played professionally in the Netherlands for 14 years, the last seven for NAC Breda. But Breda has given him permission to seek other opportunities before his contract expires this summer, and according to European media reports over the weekend, Stewart will sign with Major League Soccer soon and join United or the Dallas Burn.

"He's a definite option," United technical director Dave Kasper said. "But there are a number of options we're still looking at."

Stewart, a versatile forward and midfielder, has played in the last three World Cups and is the United States's all-time leader in Cup qualifying appearances (27) and goals (nine). He has 15 goals in 84 U.S. games overall.

United has two player allocations available -- one for missing the playoffs and the other received in a multi-player trade with the New York/New Jersey MetroStars on Dec. 23.

Hudson had been planning to talk with U.S. veteran forward Joe-Max Moore, who was released by English club Everton recently, but Moore will likely move to another team in England soon.

Meantime, United has ended talks with Italian-based forward Aldo Osorio of Argentina and doesn't appear to have a real chance of landing another targeted player, Honduran forward Milton "Tyson" Nunez.

United remains interested in Polish World Cup forward Cezary Kucharski and Chicago Fire forward Hristo Stoitchkov, but a trade for Stoitchkov can't be completed until some non-soccer issues are resolved, sources close to the situation said.

D.C. has had trade talks with New England concerning midfielder Jim Rooney and an unnamed defender, possibly former United standout Carlos Llamosa, but nothing has materialized. Former United captain John Harkes, with Columbus the past two seasons, also might become available.