Rob Manfred blasted the players' association for a "lack on cooperation" on proposed rule changes to improve Major League Baseball's pace of play.

Under baseball's labor contract, management can alter playing rules only with agreement from the union -- unless it gives one year's notice. With the one year of notice, management can make changes on its own.

Manfred said he will send a letter to the union in the coming days and plans to continue dialogue with union head Tony Clark and others in hopes of reaching agreement.

"Unfortunately it now appears that there really won't be any meaningful change for the 2017 season due to a lack of cooperation from the MLBPA," Manfred said. "I've tried to be clear that our game is fundamentally sound, that it does not need to be fixed as some people have suggested, and I think last season was the kind of demonstration of the potential of our league to captivate the nation and of the game's unique place in American culture."