Washington ? Mechanics at Northwest Airlines Corp. said Friday night they would walk off the job after negotiations with the carrier failed to reach a labor agreement by a midnight strike deadline.

The nationwide strike was set to begin at 12:01 a.m. Saturday, according to the Aircraft Mechanics Fraternal Association, the union that represents Northwest’s 4,400 mechanics, cleaners and custodians.

“Northwest wanted a strike, and now they have one,” said O.V. Delle-Femine, the union’s national director, in authorizing the walkout. “This will be difficult for our members and their families, too, but Northwest left us no choice.”

The Northwest strike is the first major labor action against a large U.S. airline since 1998, when Northwest’s pilots walked off the job for nearly three weeks.

The airline called its final offer “fair to our employees” while meeting Northwest’s needs for reduced costs.

“We intend to operate our normal schedule of domestic and international flights,” said Douglas Steenland, Northwest’s president and chief executive.

The airline said travelers can check on the status of their flights on the airline’s Web site, www.nwa.com, or on its flight information line at (800) 441-1818.

Disruptions are expected to be most deeply felt in the Midwest – especially in Detroit and Minneapolis – where Northwest operates the majority of its flights. The airline also has a significant overseas presence, with service to Asia and Europe through hubs in Tokyo and Amsterdam.

In preparation for a walkout, Northwest had lined up 1,300 replacement mechanics willing to work for lower wages, and it had said a strike would not disrupt operations. Most of the replacements have been laid off from other carriers. The rest of the work would be outsourced, the airline said.

Northwest, the nation’s fourth-largest carrier, has said it has lost more than $3.6 billion since 2001 and is on the brink of filing for Chapter 11 bankruptcy protection. The airline had sought $176 million in concessions from the mechanics as part of $1.1 billion in annual labor savings. The union said the airline wanted to slice the mechanics work force in half by using more outside contractors and to cut the pay of remaining workers by 25 percent.

Representatives from Northwest and its mechanics union negotiated through the day and evening Friday in a final effort to reach a labor agreement before a midnight strike deadline.

In talks at the National Mediation Board headquarters, both sides debated what the airline called its “last best offer,” presented to the union late Thursday evening. The union described that proposal as unacceptable.