Major League Soccer (MLS) has said 20 players and six club staff have tested positive for COVID-19 ahead of the "MLS is Back Tournament" set to begin July 8.

A total of 668 players had been tested since the resumption of full team training on June 4, with 18 testing positive ahead of traveling to the Disney World resort in Florida for the tournament, it said.

MLS said in a statement on Sunday two more players had tested positive for the coronavirus on their arrival in Orlando for the tournament, which will be held without fans and crown a winner on Aug. 11.

"Any individual who tests positive ... while in Orlando will participate in a clinical assessment by a health care provider and be moved to the isolation area of the hotel until he or she receives medical clearance," MLS said.

"While in isolation, MLS players and other staff will be in daily communication with and receive remote care ... including monitoring of symptoms and regular follow-up testing," it said.