CHICAGO -- Philadelphia defender Sheanon Williams replaced Josh Gatt on Tuesday on the U.S. roster for men's Olympic soccer qualifying, which starts this week.

Gatt was recalled by Norway's Molde after other players on the club got hurt.

Philadelphia midfielder Freddy Adu, the only holdover from the 2008 U.S. Olympic team, was picked as captain of the 20-man team. D.C. United defender Perry Kitchen was selected vice captain.

The U.S. starts Olympic qualifying in the North and Central American and Caribbean region against Cuba on Thursday, then plays Canada (Saturday) and El Salvador (Monday), with all three games at Nashville, Tenn.

The other group includes Mexico, Honduras, Panama, and Trinidad and Tobago, and is based in Carson, Calif. The top two teams in each group advance to the semifinals on March 31 at Kansas City, Kan., and the semifinal winners qualify for the London Olympics.

Qualifying is limited to players under 23, but clubs don't have to release their players. Senior national team mainstays Jozy Altidore, Timmy Chandler and Danny Williams are eligible for the U-23 team, but all get significant playing time with their European clubs and aren't likely to be released until the Olympics -- if at all.

Defender Alfredo Morales was expected to be on the qualifying roster after appearing at the team's February training camp and starting an exhibition game against Mexico. But Hertha Berlin, which is fighting to avoid relegation, apparently would not release him.

If the Americans qualify for London, they will be able to add three players over the age of 23. Clint Dempsey and Landon Donovan both have expressed interest in playing, though they also would need their clubs' permission. Dempsey is with Fulham in the English Premier League, while Donovan plays for MLS champion Los Angeles.

The roster:

• Goalkeepers: Bill Hamid (D.C.), Sean Johnson (Chicago)

• Defenders: Perry Kitchen (D.C.), Ike Opara (San Jose), Kofi Sarkodie (Houston), Zarek Valentin (Montreal), Jorge Villafana (Chivas USA), Sheanon Williams (Philadelphia)

• Midfielders: Freddy Adu (Philadelphia), Joe Corona (Tijuana, Mexico), Mix Diskerud (Ghent, Belgium), Jared Jeffrey (Mainz, Germany), Amobi Okugo (Philadelphia), Michael Stephens (Los Angeles)

• Forwards: Juan Agudelo (New York), Terrence Boyd (Borussia Dortmund, Germany), Teal Bunbury (Kansas City), Joe Gyau (Hoffenheim, Germany), Brek Shea (Dallas), Tony Taylor (Estoril Praia, Portugal)