NEW YORK – The Professional Referee Organization (PRO) has been unable to reach a labor agreement with the referees, and Major League Soccer’s opening weekend will be played with replacement officials. PRO had offered to use the current referees for the start of the season while negotiations continued, but the referees union rejected that proposal.

PRO will use replacement officials for the eight MLS matches played this weekend and until an agreement is reached with the Professional Soccer Referees Association (PSRA). The lockout officially began on Friday morning.

“We have made a substantial proposal to the Professional Soccer Referees Association and believe it is very fair and reasonable,” PRO general manager Peter Walton said in a statement. “Our proposal represents a significant increase above current compensation for referees and places them above the average for officials around the world. We are disappointed it has been rejected.”

The replacement officials attended a preseason training last week as part of PRO’s contingency plan for a work stoppage. Seven of the eight officials working this weekend have officiated MLS matches or FIFA international matches in the past.

Irishman Alan Kelly (right) will officiate the league’s season opener between the Seattle Sounders and Sporting Kansas City on Saturday (3 pm ET, NBCSN). Kelly was first appointed to the FIFA list in 2002 and has since officiated in the UEFA Champions League and World Cup qualifying matches in 2006, 2010 and 2014.

Also included in this weekend’s assignments are former MLS Referee of the Year Abbey Okulaja (Vancouver vs. New York), and former MLS referees Ramon Hernandez (Houston vs. New England) and Jorge Luna (FC Dallas vs. Montreal).

“We have high confidence in the qualifications of our replacement officials and can ensure our fans, clubs and players that all games will be officiated at a professional standard that protects the integrity of our matches and the safety of our players,” Walton said.

“Although it is regrettable that the Professional Soccer Referees Association rejected PRO’s offer to continue with the current referees while negotiations continue, we have great confidence in the plan for replacement referees that PRO has put in place,” MLS president and deputy commissioner Mark Abbott said when contacted by MLSsoccer.com.

PRO was created in 2012 with the goal of developing and improving referees in North America. Walton said that his organization had hoped to avoid a lockout and its leaders suggested a path that would avert a work stoppage.

“We had suggested a no strike/no lockout agreement for a reasonable period in an effort to keep the negotiations going but that was rejected by the PSRA,” Walton said. “Since they will not give us a guarantee they will not go on strike immediately prior to our matches, we are left in a position where we must use replacement officials to ensure that the MLS games are played as scheduled this weekend.”