JUPITER, Fla. -- Despite a long day of conversations between MLB and the MLBPA on Sunday, the sides still remain far apart on a new collective bargaining agreement, a union source told ESPN.

The six-plus hours of meetings came a day before a league-imposed deadline that will trigger the cancellation of regular-season games. If the sport doesn't have a new collective bargaining agreement by the end of negotiations on Monday, Opening Day on March 31 will be canceled along with potentially a week's worth of games.

The league has indicated it wants about four weeks of spring training before opening the season, hence the Feb. 28 deadline in order to play on March 31.

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The sides will meet again Monday morning for an eighth consecutive bargaining session. A union source indicated it's ready to stay as long as it takes to reach an agreement. The league has said the same. A league source called Sunday a "productive" day of conversations, but no new proposals on core economics were exchanged, nor were any outstanding issues resolved.