Major League Baseball and the players' association have submitted letters of intent to seek new labor terms as the Dec. 1 expiration of the sport's collective bargaining agreement approaches.

The notices, sent to the Federal Mediation and Conciliation Service, are a formality under federal labor law required during every negotiation. They were exchanged Aug. 26 by MLB deputy commissioner Dan Halem and Ian Penny, the general counsel of the Major League Baseball Players Association.

Under federal labor law, a CBA may not be modified or terminated unless a side seeking to make changes notifies the other side more than 60 days in advance of expiration and tells the mediation service within 30 days of giving notice.

Baseball has not had a work stoppage since the 7½-month strike that wiped out the 1994 World Series. The sides reached agreements without work stoppages in 2002, 2006, 2011 and 2016, but the relationship has become more strained in recent years as salary escalation has slowed. Salaries in 2021 are likely to fall between $3.6 million and $3.7 million, down from just under $4.1 million in 2017.

Negotiations have proceeded slowly, and both sides appear to be bracing for a lockout that could start either on Dec. 1 or when players are scheduled to report to spring training in February.

MLB and the MLBPA are also slated to start a grievance hearing Monday over the union's claim that the 2020 pandemic-affected season was too short. If the union prevails, MLB might be liable for hundreds of millions of dollars in damages.

The Associated Press contributed to this report.