[OLYMPIC COUNTDOWN] U.S. under-23 national team head coach Caleb Porter named an initial roster of 19 players who will assemble for training camp Tuesday to begin final preparations for the Concacaf Men's Olympic Qualifying tournament that kicks off for the Americans March 22 at LP Field in Nashville, Tenn. Columbus Crew midfielder Dilly Duka's injury over the weekend and Hertha Berlin's seeming reluctance to release Alfredo Morales left one spot up in the air.

Duka pulled a hamstring early in the first half of the Crew's 2-0 loss at Colorado. An MRI revealed no major damage and he hoped to return to action in two weeks.

Morales was the only starter from the 2-0 win over Mexico on Feb. 29 not called up. Duka and Tony Taylor of Portugal's Estoril were the only subs not in the 19-player roster.

The 20th spot is expected to go to a midfielder.

The official roster will be finalized March 20, the due date for all participating teams to submit their rosters to Concacaf.

Six U-23 players are based at foreign clubs: midfielders Joe Corona (Tijuana), Mix Diskerud (Gent) and Jared Jeffrey (Mainz) and forwards Josh Gatt (Molde), Joe Gyau (Hoffenheim) and Terrence Boyd (Borussia Dortmund).

Boyd, who made his debut for the full team when he came on as a substitute in the USA's 1-0 victory against Italy, will report March 21 to Nashville.

Seven other players, including 2008 Olympian Freddy Adu, have at least one cap with the full team.

Senior national team players Jozy Altidore (another 2008 Olympian) and Danny Williams, who started against Italy, and Timmy Chandler, are eligible as U-23 players but were not called up.

Gatt, who plays for Norwegian champion Molde, returns after injuries limited the time he has had in the U-23 camp.

Porter on the qualifying roster: "Obviously, our mission is to qualify for the 2012 summer Olympics and this roster is a culmination of a long process to select what we feel is the best team this country has to offer in the U-23 age group. For the past four training camps we have been comprehensively evaluating the most talented personnel available from an extensive player pool comprised of professional players on clubs in this country and abroad. We always keep in mind it's most important to find the best mix collectively so that we can build a cohesive team capable of accomplishing our goal. I feel very confident in this collection of players and their ability to execute the playing style we believe will best represent their talents and get us to London."

U.S. Roster:
GOALKEEPERS (2): Bill Hamid (D.C. United), Sean Johnson (Chicago Fire)
DEFENDERS (6): Josh Gatt (Molde/NOR), Perry Kitchen (D.C. United), Ike Opara (San Jose Earthquakes), Kofi Sarkodie (Houston Dynamo), Zarek Valentin (Montreal Impact), Jorge Villafana (Chivas USA)
MIDFIELDERS (6): Freddy Adu (Philadelphia Union), Joe Corona (Tijuana/MEX), Mix Diskerud (Gent/BEL), Jared Jeffrey (Mainz II/GER), Amobi Okugo (Philadelphia Union), Michael Stephens (LA Galaxy)
FORWARDS (5): Juan Agudelo (New York Red Bulls), Terrence Boyd (Borussia Dortmund II/GER), Teal Bunbury (Sporting Kansas City), Joe Gyau (Hoffenheim II/GER), Brek Shea (FC Dallas)