Eddie Johnson is set to retire because of a heart ailment. Joe Nicholson/USA TODAY Sports

Major League Soccer has voided the contract of D.C. United forward Eddie Johnson, according to the Washington Post.

Johnson, 31, is set to retire after a heart ailment was discovered late last year.

"Nothing has changed," United coach Ben Olsen told the Post. "Eddie is out with a heart condition."

The former U.S. international missed most of training camp and has not played this season.

The Post reported that D.C. United was unaware of Johnson's illness when they acquired him from the Seattle Sounders before last season.

With uncertainty surrounding when the Sounders knew of the ailment -- athletic heart syndrome, the Post says -- the league has reportedly canceled his contract.

The move allows D.C. to replace Johnson on the squad and free up salary cap space while the league works out details before officially announcing his retirement.

"A lot of people are looking after Eddie and trying to figure out what's the next move for him," Olsen told the Post.

Johnson began his MLS career in 2001 and played for FC Dallas for five years before moving to Kansas City. He was signed by Fulham in the Premier League before returning to MLS in 2012 with Seattle. He scored seven goals for D.C. United last season.

Johnson made 63 appearances for the United States national team.