NEW YORK — Major League Baseball plans to unilaterally issue a 60-game schedule for its shortest season since 1878 after the players’ association rejected a negotiated deal of the same length, putting the sport on track for a combative return to the field amid the coronavirus pandemic.

Commissioner Rob Manfred and union head Tony Clark met last week and outlined plans that included expanding the playoffs from 10 teams to 16, widening use of the designated hitter to National League games and an experiment to start extra innings with a runner on second base. But the latest version of the deal proposed by MLB was rejected by the Major League Baseball Players Association’s executive board in a 33-5 vote on Monday.

Those innovations now disappear.

“Needless to say, we are disappointed by this development,” MLB said in a statement. “The framework provided an opportunity for MLB and its players to work together to confront the difficulties and challenges presented by the pandemic. It gave our fans the chance to see an exciting new postseason format. And, it offered players significant benefits.”

MLB’s control owners approved going unilaterally with the 60-game schedule in ballparks without fans if the final arrangements can be put in place, a person familiar with the decision told The Associated Press. The person spoke on condition of anonymity because no announcement had been made.

MLB asked the union to respond by 5 p.m. EDT Tuesday as to whether players can report to training by July 1 and whether the players’ association will agree on the operating manual of health and safety protocols. The schedule would be the shortest since the National League’s third season.

The MLPBA Executive Board released a statement Tuesday saying it will review the rules for safety protocols and is fully committed to abiding by the commissioner’s mandate.

Given the need for three days of virus testing and 21 days of workouts, opening day likely would be during the final week of July. MLB already has started to investigate charter flights that could bring players back from Latin America, another person told the AP, also on condition of anonymity because no announcements were made.