The Professional Referee Organization, which manages game officials for the U.S. Soccer Federation and MLS, notified the Professional Soccer Referee Association of the lockout and said replacement officials will be used.
PRO said the union, which was formed last year, rejected a no strike-no lockout agreement that management had proposed. The sides have bargained since July without reaching a deal on a labor contract.
"Our proposal represents a significant increase above current compensation for referees and places them above the average for officials around the world," said PRO general manager Peter Walton, an English Premier League referee from 2003-12.
PRO said in the 1 1/2 years since its formation, it had increased full-time officials from two to nine and added 11 part-time officials.
The PSRA has filed unfair labor practice charges accusing the PRO of bad-faith bargaining and making threats against its members.
"We have requested a plethora of information, including financials, that PRO and MLS have refused to provide, instead demanding we take their pleas of poverty at face value," said Lukas Middlebrook, a lawyer for the union.
Replacements this weekend include former Ireland referee Alan Kelly (Kansas City-Seattle); former Greece referee Ioannis Stavridis (Philadelphia-Portland); current Puerto Rico referees Javier Santos (Salt Lake-Los Angeles) and William Anderson (Chicago-Chivas USA); former MLS referees Abbey Okulaja (New York-Vancouver) and Ramon Hernandez (New England-Houston); former MLS fourth official Jorge Luna (Montreal-Dallas); and current North American Soccer League referee Andres Pfefferkorn (Columbus-D.C.). Kelly is a veteran of five World Cup qualifiers and three Champions League matches.