Striking mechanics at Northwest Airlines Corp. walked away from talks on Sunday, refusing to say if they would return to the bargaining table before a Tuesday deadline for when Northwest says it will start hiring permanent replacements.

Union officials said they had agreed to demands for wage concessions and layoffs but could not agree on severance packages and work rules, so they abandoned efforts to negotiate a proposal that they could put to members for a vote.

Northwest spokesman Kurt Ebenhoch said mediators told the airline that the union had "discontinued negotiations."

Union negotiations spokesman Jeff Mathews said, "There's no negotiations scheduled at this time." He declined to elaborate.

The carrier has kept flying through the strike that began on Aug. 20. The negotiations had restarted Thursday.

The union says Northwest wants to keep only 1,080 mechanics' jobs and eliminate the aircraft cleaner and custodian positions represented by the union. It says that would mean eliminating 3,181 positions that existed before the strike.

Northwest's proposal would save it $203 million a year, up from the $176 million it sought before the strike began Aug. 20. Mechanics made their own proposal Saturday.

Northwest increased the amount in annual labor cost savings it is seeking to $1.4 billion from $1.1 billion, saying rising fuel prices forced it to raise the target.

Northwest has said time is running out for it to avoid filing for bankruptcy protection.