Updated

Flight attendants at Northwest Airlines Corp. said their talks are at an impasse and asked to be released from further negotiations, one more step toward a potential strike the union has been pushing for since last month.

By asking the National Mediation Board to declare an impasse, flight attendants put their attempt to strike onto a second track after a federal judge blocked the first one.

If the board agrees that more talks are pointless, it could start a 30-day clock ticking toward a strike. No talks have taken place recently.

The union planned random, unannounced walkouts after Northwest imposed pay cuts and work rule changes on July 31. But a federal judge blocked the walkouts, saying flight attendants first need to run through the negotiations and mediation required by the Railway Labor Act, which governs unionized airline labor.

Flight attendants have said they will appeal that ruling. But by asking for release from negotiations, they put their dispute back into the territory of the Railway Labor Act. The National Mediation Board has ordered both sides to give it an update in Washington on Tuesday.

Northwest, which is reorganizing under Chapter 11 protection, had a bankruptcy judge's permission to cut pay and impose change work rules after flight attendants twice rejected negotiated settlements. It said it needs the $195 million in changes so it can emerge from bankruptcy.

Northwest has said it wants to negotiate. The airline "is looking at a number of ways to structure an agreement with our flight attendants and welcomes any input from AFA," the airline said in a statement.

But the union has refused to go to the table, saying talks would be pointless unless they have the right to strike.

"We've had two agreements rejected by the membership, and the employer insists on the same fundamental terms, therefore unless management has a meaningful proposal to make we think we're at an impasse," said David Borer, general counsel for the Association of Flight Attendants.

"When management unilaterally cut flight attendant pay, benefits and work rules, they mocked the integrity of the NMB's role in promoting consensual resolution of labor disputes," AFA-CWA President Patricia Friend said in a prepared statement. "Northwest management has made every attempt to stall negotiations and hang on to the concessions that they forcibly took in bankruptcy court."