(CNN) -- NBA players rejected Monday the league's latest offer in a dispute over a collective bargaining agreement, a move that leaves hopes of salvaging the remainder of the already-shortened season in doubt.
Calling the offer "extremely unfair," union director Billy Hunter said the National Basketball Players Association is beginning the process to disband and is prepared to file antitrust action against the NBA as early as Monday afternoon.
"We as a group of players after two years of making a genuine and concerted effort to try and close a collective bargaining agreement with our teams and with the league, we've come to the conclusion today that that process has not worked for us," said Derek Fisher, president of the players association.
"It has not put us in a position to get and negotiate the fair deal that we've been working to try and complete."
Fisher called the decision to reject the offer and disband a unanimous one.
"This is the best decision for the players," he said, adding in a message to fans that "we have not chosen to be in this position. A lockout continues to be something that is imposed on us by the league and by the owners. This is not a strike."
The NBA had already canceled games through December 15. The owners' most recent proposal had been for a 72-game season starting on that date.
Asked whether the 2011-2012 season will be wiped out, NBA Commissioner David Stern told ESPN that 30 days would be needed between an agreement and the beginning of games, "and now we have no one to negotiate with."
He put it in plainer terms in a written statement issued after the talks broke down, saying "the 2011-12 season is now in jeopardy."
Stern blamed Hunter for the developments, telling ESPN that Hunter "has decided to ... deprive his union members of an enormous payday."
In his written statement, Stern accused the players' association of "not bargaining in good faith" since talks began in February 2010.
Team owners locked out players in early July as the two sides tried to hammer out a new agreement. Stern has said the previous season was not profitable for most of the league's 30 owners, who are seeking a bigger share of league revenues.
The owners' latest offer on Friday called for a 50-50 split of revenues between the owners and players. On Sunday, Stern urged players to accept what he called "a fair compromise of the issues between us," according to the memo posted on NBA.com.
In addition to the revenue issue, points of contention in the negotiations include the owners' plan to strengthen a salary cap and the players' demand to raise the average salary.
Stern told ESPN that the players "walked away from an offer that would not have had a rollback from the existing contract, would have had guaranteed contracts" and would have raised the average salary from around $5 million a year to more than $7 million.
A previous lockout in the NBA lasted 204 days, from July 1998 to January 1999, before a new collective bargaining agreement was reached by both sides. That agreement expired in June, sparking the latest developments.