(CNN) -- The ongoing labor dispute between the professional basketball players' union and the league ratcheted up a notch Tuesday as the NBA said it filed a lawsuit against the players.
The NBA also announced Tuesday that it has filed an unfair labor practice charge with the National Labor Relations Board along with the lawsuit, which was filed in federal court in New York.
These moves have one NBA expert saying the labor struggle is putting the start of the NBA season in danger.
"This is just one more log on the fire that is threatening to consume the whole NBA season," said David Aldridge, a reporter for NBA TV. "I am not optimistic that season will start on time."
Both actions are reactions to recent threats by the players' union that were hampering negotiations, the NBA said in a statement.
"These claims were filed in an effort to eliminate the use of impermissible pressure tactics by the union which are impeding the parties' ability to negotiate a new collective bargaining agreement," said NBA Deputy Commissioner and Chief Operating Officer Adam Silver.
The NBA began a lockout of its players in early July.
NBA Commissioner David Stern has argued that the last season was not profitable for most of the league's 30 owners and there was a need for some cost-cutting help from players.
The league lost as much as $300 million in the 2010-11 season, Stern has said.
One of the battles has been around the owners not agreeing to the players union's call for an average $7 million player salary in the sixth year of a new labor deal.
The current salary average is about $5 million.
Aldridge said other big issues are a fight over whether the NBA will strengthen its salary cap and a move by the owners to get a bigger share of revenues.
The last work stoppage occurred in 1998.