Union chief Billy Hunter said Thursday "it's obvious the lockout will happen tonight" after players and owners failed to reach a new collective bargaining agreement, potentially putting the 2011-12 season in jeopardy.
Despite a three-hour meeting Thursday and a final proposal from the players, the sides could not close the enormous gap that remained in their positions.
"The gap is too great," Hunter said.
The CBA expires at midnight, after which all league business is officially on hold, starting with the free agency period that would have opened Friday.
Commissioner David Stern said "with some sadness" he would recommend later Thursday to the labor relations committee that the first lockout since the 1998-99 season be imposed.
"Needless to say we're disappointed that this is where we find ourselves," Deputy Commissioner Adam Silver said.
Hunter said he hopes the two sides will meet again in the next two weeks.
The last lockout reduced the 1998-99 season to just a 50-game schedule, the only time the NBA missed games for a work stoppage. Hunter said it's too early to be concerned about that.
"I hope it doesn't come down to that. Obviously, the clock is now running with regard to whether or not there will or will be a loss of games, and so I'm hoping that over the next month or so that there will be sort of a softening on their side and maybe we have to soften our position as well."
The players' association seems unlikely, at least for now, to follow the NFLPA's model by decertifying and taking the battle into the court system, instead choosing to continue negotiations. Hunter said last week he felt owners believe the 8th U.S. Circuit Court of Appeals in St. Louis, which is debating the legality of the NFL's lockout, will uphold employers' rights to impose lockouts.
The NBA's summer league in Las Vegas already has been canceled, preseason games in Europe were never scheduled, and players might have to decide if they want to risk playing in this summer's Olympic qualifying tournaments without the NBA's help in securing insurance in case of injury.
Training camps usually open the last week of September and the regular season about a month later.