D.C. United midfielder Chris Pontius and Birmingham City midfielder-defender Jonathan Spector were added to the U.S. national soccer team roster ahead of friendlies against Costa Rica on Friday and Belgium next Tuesday, Coach Juergen Klinsmann announced Monday.

They replaced a pair of injured MLS defenders: FC Dallas’s Zach Loyd and Chivas USA’s Heath Pearce, who are sidelined with hamstring ailments.

In addition, Fulham midfielder-forward Clint Dempsey is suffering from back spasms and won’t join the squad until it arrives in Brussels.

Pontius, in his third season, has scored a career-high seven goals and contributed two assists. His previous U.S. call-up came in early 2010 . For this stint, he joins United teammate Bill Hamid at camp at Home Depot Center in Carson, Calif., site of Friday’s match against the Ticos (11 p.m. ET, ESPN2, Galavision, ESPN3.com).

With United off until Sept. 10, neither player will miss any league matches.

The Belgium game will be shown on ESPN and ESPN3.com, starting at 2:30 p.m. ET.

For the updated USA roster.....

GOALKEEPERS: Bill Hamid (D.C. United), Tim Howard (Everton).

DEFENDERS: Carlos Bocanegra (Rangers), Edgar Castillo (Club America), Timmy Chandler (Nuremberg), Clarence Goodson (Brondby), Michael Orozco Fiscal (San Luis), Tim Ream (New York Red Bulls), Jonathan Spector (Birmingham).

MIDFIELDERS: Maurice Edu (Rangers), Fabian Johnson (Hoffenheim), Sacha Kljestan (Anderlecht), Jeff Larentowicz (Colorado Rapids), Chris Pontius (D.C. United), Robbie Rogers (Columbus Crew), Brek Shea (FC Dallas), Jose Torres (Pachuca).

FORWARDS: Juan Agudelo (New York Red Bulls), Jozy Altidore (AZ Alkmaar), Teal Bunbury (Sporting Kansas City), Landon Donovan (Los Angeles Galaxy).