As Major League Baseball’s lockout enters its third month, and with minimal progress in negotiations with the MLB Players Association, the league is requesting a federal mediator to assist in reaching an agreement, multiple sources with knowledge of the situation said Thursday, confirming an ESPN report.

Because mediation is a voluntary process, the players association must agree to participate. The union declined to comment on its intentions, though it has not found mediation to be a successful solution in the past.

MLB has been in contact with the Federal Mediation and Conciliation Service, an independent government agency that specializes in helping to resolve labor disputes. The FMCS, led by mediator Scot Beckenbaugh, intervened in the 2012 NHL lockout and played a central role in getting a deal. But former FMCS director William Usery couldn’t bring MLB players and owners together during the 1994-95 strike, with then-union leader Tom Glavine describing his proposals as “outrageous.”

“We were willing to compromise, and we have shown that. But Mr. Usery’s proposal was outrageous in many instances,” Glavine said at the time. “We’d be giving away things we’ve gone on strike for previously. Mr. Usery couldn’t answer any questions about what a lot of his proposal meant.”

In the latest bargaining session on core economics, a 90-minute meeting Tuesday that was characterized as “heated,” the players made two proposals that did little to advance the talks. MLB hasn’t scheduled a meeting to make counterproposals, and it’s unclear if it intends to do so before receiving the players’ answer on mediation.

Regardless, with pitchers and catchers scheduled to report to most camps on Feb. 15, it’s all but certain that spring training won’t open on time. If an agreement isn’t reached by the end of the month, it likely will result in a delayed start to the season and perhaps even an abbreviation of the 162-game schedule.

The owners voted to direct commissioner Rob Manfred to enact a lockout on Dec. 2 after the expiration of the collective bargaining agreement. The sides didn’t meet on economic issues for the next 42 days. Four meetings over the last few weeks have paved virtually no ground toward an agreement.

In particular, the sides are far apart on issues related to minimum salary, arbitration eligibility, draft-pick compensation that is tied to free agency, and the competitive-balance tax. The players, whose average salary has declined in each of the last four years, are seeking major changes to the economic system. The league/owners mostly want the status quo, in addition to an expanded playoff format.