Commissioner David Stern, left, and Deputy Commissioner Adam Silver were among those in the 12-hour discussions on Wednesday and then again into Thursday evening. (John Minchillo/Associated Press)

With unsettling consequences awaiting them should they fail to reach an agreement, representatives for the NBA and players’ union met again on Thursday in an effort to salvage what remains of an already-shortened season.

After negotiating for nearly 11 hours, the sides were unable to produce a settlement for a collective bargaining agreement, but the NBA presented a proposal to the players that, if approved by next week, would possibly result in a 72-game season that would begin on Dec. 15.

NBA Commissioner David Stern refused to refer to the proposal as the league’s “last best offer,” but intimated that it was the case after conferencing with members of the owners’ labor relations committee.

“There comes a time when you have to be through negotiating and we are. We have done everything possible that was possible to do,” Stern said. “There is nothing left to negotiate about.”

Derek Fisher and Billy Hunter, the president and executive director, respectively, of National Basketball Players Association, expressed disappointment that they were unable to close the gap on six salary cap and luxury tax system issues that have divided the sides throughout the four-month labor stalemate. The union plans to have player representatives from the 30 teams to convene in New York on Monday or Tuesday to review the latest offer and come back to the NBA with a decision.

“We still would like to continue to negotiate to get a deal done; right now is not that time,” Fisher said, adding that the league made some revisions from the proposal that players rejected earlier this week but “not enough to entice us to finish this out. . . . It does not meet us entirely on the system issues that we felt were extremely important to close this deal out.”

Players have expressed willingness to accept a 50-50 split of the nearly $4 billion in basketball-related revenues but only in exchange for fewer restrictions on high-spending teams. But the owners have stressed the importance of a favorable system over the revenue split, which has made a compromise difficult. The NBA is seeking changes it believes would ensure competitive balance.

“We recognize that in order to have the kind of competitive balance we want, it restricts player movement to a certain degree,” NBA Deputy Commissioner Adam Silver said. “I understand from the union’s standpoint, it’s a difficult pill to swallow right now but once again, we will be proven right and this will be a better league for the players, the teams and the fans. . . . Fans can believe that a well-managed team, regardless of market size, regardless of how deep the owners’ pockets are, will be in a position to compete for a championship.”

After a lengthy negotiation with federal mediator George Cohen concluded early Sunday, the owners presented a proposal that would allow players to receive between 49 percent and 51 percent of revenues. But the deal also limited the ability of teams that pay the luxury tax from signing free agents, prohibited them from doing sign-and-trade deals and enhanced penalties for teams that spend more than $5 million over the luxury tax threshold.

The owners appeared to make incremental movement toward the players on Thursday but Hunter added that there were more than 30 other “B-list” issues that still need to be addressed.

“It’s not the greatest proposal in the world,” Hunter said. “But I owe that I have an obligation to at least present it to membership.”

If the sides still can’t come together, players are reportedly prepared to quickly move toward the decertifying the union or possibly, issuing a disclaimer of interest, with either option allowing them to file antitrust litigation that would likely put the entire season in jeopardy.

“We don’t expect them to like every aspect of our revised proposal. Many teams don’t like every aspect of our proposal,” Stern said. “I would not presume to project or predict what the union would do. I don’t have a crystal ball. I can hope. My hope is that the events of next week will lead us to a 72-game schedule starting on Dec. 15.”

The NFL lockout lasted 132 days and resulted in the cancellation of just one exhibition game. The NBA lockout entered its 134th day on Friday and has led to the loss of the preseason and 221 regular season games through this month.

The latest round of talks was spurred when Stern set a Wednesday deadline for the players to accept the league’s latest proposal or receive a harsher alternative. Stern agreed to stop the clock and said the past two days had “desired impact” of getting the two sides back in the room get a deal. While giving the union time to process the offer, Stern threatened a “reset” deal that would offer the players 47 percent basketball-related income and a hard salary cap if the current proposal was rejected.

The owners were represented on Thursday by the same five men as the day before: Stern, Silver, labor committee chairman and San Antonio owner Peter Holt and attorneys Rick Buchanon and Daniel Rube. Union executive committee members Chris Paul, Keyon Dooling, Matt Bonner, Theo Ratliff and Etan Thomas joined Hunter, Fisher, vice presidents Maurice Evans and Roger Mason Jr., economist Kevin Murphy and attorney Jeffrey Kessler.