SEATTLE (AP) - Despite a 48-hour contract extension, negotiations between Boeing Co. and Machinists union officials have failed and the union declared: "The strike is on!"

The Machinists bargain for about 25,000 aircraft assembly workers in the Puget Sound area, 1,500 in the Portland, Ore. area and about 750 in Wichita, Kan.

Picket lines went up in Wichita early Saturday and West Coast machinists were set to walk out at 12:01 a.m. PDT.

This is the Machinists' second strike in as many contract negotiations. They struck for 24 days in 2005.

"We have struck before. We know what to expect," said Darrick Kessler, a modification mechanic in Wichita with 11 years at Boeing. "It is a business decision on our part, a business decision on their part."

The company said it would not try to assemble planes during the strike.

Boeing spokesman Tim Healy said the company is open to further discussion, but both sides were too far apart to reach agreement. He added no additional talks were scheduled.

Union members on Wednesday voted 80 percent to reject Boeing's final three-year contract offer and 87 percent to go on strike, mainly over job security. Both sides agreed to the extension at the request of Gov. Chris Gregoire and federal mediators.

Negotiators for Boeing and the machinists jetted off to a Disney resort in Florida for talks following the extension, in part so Tom Buffenbarger, International Association of Machinists international president, could participate. Buffenbarger was at the resort for an IAM convention.

Tom Wroblewski, president of Machinists District Lodge 751, declared in a statement Friday that Boeing had "disrespected the finest aerospace workers anywhere on the planet" by failing to meet machinists' expectations.

"Despite meeting late into the night and throughout the day, continued contract talks with the Boeing Company did not address our issues," he added.

"Over the past two days, Boeing, the union and the federal mediator worked hard in pursuing good-faith explorations of options that could lead to an agreement," Scott Carson, president and CEO of Boeing Commercial Airplanes, said in a statement. "Unfortunately the differences were too great to close."

Boeing operations in Washington, Oregon and Kansas will remain open, Carson said. Employees, such as engineers, who are not represented by the Machinists are expected to report for work as usual, he added.

During the strike, Carson said the company does not intend to assemble airplanes, but would deliver completed planes and supply customers with spare parts.

"Boeing and its workforce are a critical part of the health of the state economy," Gregoire said in a statement. "I urge both parties to continue working on a resolution and settle the strike as quickly as possible. I will continue to monitor the situation closely."

Boeing's "best and final" three-year offer, presented Aug. 28 after talks that began May 8, included bonuses totaling at least $5,000 and averaging $6,400, raises averaging 11 percent, pension increases and a 3 percent cost-of-living adjustment - $34,000 in average pay and benefit gains per employee, according to the company.

Machinists union member Scott Daniels, 41, a facility worker at Boeing's Renton plant, was part of a crew making strike signs Friday night at a union hall.

"We're not greedy, we just want a piece of the pie," he said. "They offer us bonuses. We don't want bonuses." Machinists do want an improved 401k and improved vacation, he said.

The average Boeing machinist earns $27 an hour, or about $56,000 a year, before overtime and incentives.

Analysts have said a strike could cost Boeing about $100 million per day in deferred revenue. During the last strike, Boeing was unable to deliver more than two dozen airplanes on schedule.