MLS and its referees edged closer to a work stoppage Tuesday after the sides failed to make progress in efforts to reach a collective bargaining agreement before the season openers this weekend.

Steve Taylor, lead negotiator for the Professional Soccer Referees Association, said management has “threatened a lockout. I expect that call later today from Peter Walton,” general manager of the Professional Referee Organization, which oversees officiating on behalf of MLS and the U.S. Soccer Federation.

“They have not made any significant movement in our direction on economic or non-economic issues that are still outstanding,” Taylor said after four hours of meetings in New York. The sides also met for five hours Monday. No additional meetings are scheduled this week.

The union’s seven-member board has planned a conference call Wednesday night to discuss the situation and weigh options.

Taylor, however, said he expects PRO to make the next move, calling for a lockout that would preempt a training camp in Florida for referees assigned to this weekend’s matches.

Meantime, Taylor said PRO conducted a training camp in Dallas last weekend for potential replacement referees. The group includes former MLS officials as well as foreign referees.

Walton was not immediately available to comment.

“We are absolutely in a position to have a contingency plan in the event those discussions don’t end positively,” MLS Commissioner Don Garber said of the CBA negotiations during a Q&A session with fans and media earlier Tuesday. “Nothing is going to stop us from having a strong opening.”

The prospects of replacements officials “pains me,” Taylor said. “The potential for disaster is great. I’m concerned about the health and welfare of the players in games officiated by referees who won’t have a handle on games at this level.”

Aside from the negotiations, the union filed a complaint with the National Labor Relations Board two weeks ago, claiming a PRO representative threatened at least 10 referees with retribution if they continued with union activities. In a previous complaint, the PSRA alleged PRO failed to respond to several information requests; engaged in “regressive bargaining by withdrawing a number of tentative agreements without good cause;” failed to “bargain in good faith;” and was not available for meetings.

The referees unionized last year and have had more than 25 meetings with PRO in efforts to reach their first collective bargaining agreement.

Last year, PRO’s budget for salaries and match fees was an estimated $2.1 million. PRO employs 20 full- and part-time match officials and an additional 56 who are compensated on a per-game basis. These 76 officials comprise the entire pool of people eligible to work matches as referees, assistant referees and fourth officials in MLS.

MLS is PRO’s primary financial backer, with the USSF contributing a smaller share.

Neither side has been willing to go into detail about their respective proposals.

“What is on the table is a fair deal,” Walton said several weeks ago, adding that “we stand above,” compared to referee compensation globally.