NEW YORK — With one final proposal and one last ultimatum, the NBA put the wheels in motion Thursday for a delayed season that could begin Dec. 15, or perhaps not at all.

After 23 hours of talks over two days, the league delivered a revised offer to the players union, with the clear goal of seeing a vote from the full membership. If the players approve the offer, a 72-game season will commence in mid-December. If union leaders reject the deal — or if the 430-plus players vote it down — it will be replaced by a significantly worse proposal, one that virtually guarantees cancellation of the 2011-12 season.

Commissioner David Stern specifically avoided terming this the NBA's last, best offer, but that was clearly what it was.

"We have made our revised proposal, and we're not planning to make another one," Stern said, adding, "There's really nothing left to negotiate about."

The offer is based on a 50-50 split of league revenues, which the union is resigned to accepting. But it also contains a range of new restrictions on player movement and team payrolls, all of which the union opposes.