NEW YORK -- The union for NBA players filed an unfair labor practices complaint with the National Labor Relations Board on Tuesday, seeking an injunction that would prevent owners from imposing a lockout when the current collective bargaining agreement expires June 30.
The players' union, less than a month after receiving the latest formal proposal from the owners, is accusing the owners of negotiating in bad faith.
The complaint, in part, alleges the NBA is "making harsh, inflexible, and grossly regressive 'takeaway' demands that the NBA knows are not acceptable to the Union."
The complaint further alleges the NBA is engaging in "classic 'take it or leave it' and surface bargaining" with the intent of running out the clock on the CBA, "until the NBA locks out the represented employees in order to coerce them into accepting the NBA's harsh and regressive demands."
The NBA issued a statement in response to the complaint.
"There is no merit to the charge filed today by the Players Association with the National Labor Relations Board, as we have complied -- and will continue to comply -- with all of our obligations under the federal labor laws. It will not distract us from our efforts to negotiate in good faith a new collective bargaining agreement with the Players Association," the league said in a statement.
Sources have told ESPN.com that the players were so infuriated by the owners' latest proposal, which seeks a nearly 40 percent rollback in existing contracts over three years and a hard salary cap, that the union would explore a variety of legal options before presenting another formal counterproposal.
The sides are scheduled to have a formal bargaining session with the owners' labor committee and the players' executive board during the NBA Finals in Dallas or Oklahoma City.
Tuesday's filing with the NLRB marked a sharp turn in negotiating strategy after the sides had held several rounds of informal discussions over the past several weeks.
The filing comes just eight days after the death of the union's No. 2 executive, Gary Hall, and moves the dispute into a different forum through which the players will attempt to gain negotiating leverage.
In a statement, the union said the unfair practices included failure to bargain in good faith, demanding huge financial takeaways from prior contracts without offering concessions in return, bypassing the Union to deal directly with players and threatening an unlawful lockout.
"We have urged the Board to investigate this matter quickly and to seek an injunction against the NBA's unlawful bargaining practices and its unlawful lockout threat," the union said.
Just a week ago, NBA deputy commissioner Adam Silver struck a conciliatory tone in discussing the negotiations, going so far as to say it would be "irrational" for the sides to allow the dispute to evolve into a work stoppage.
The NBA has not had a protracted labor dispute since the summer of 1998, when a lockout extended into February of 1999 and forced the league to play a 50-game season.
But owners have taken a hard-line stance in the current negotiations, saying they need a completely restructured system to give them a bigger slice of the financial pie. Commissioner David Stern said the league expects to lost $300 million in the current season.
Chris Sheridan covers the NBA for ESPN.com.