EVERETT — A last-ditch effort to stave off a Machinists’ strike at the Boeing Co. failed on Friday.

Nearly 24,000 workers who build Boeing jets in the Puget Sound region will go on strike at 12:01 Saturday morning.

More than 87 percent of Machinists voted on Wednesday to go on strike, but union leaders gave Boeing a 48-hour reprieve to devise a three-year labor contract that meets the Machinists’ demands. A federal mediator took part in the two-day contract talks with negotiatiors for Boeing and the union. But the two sides remained too far apart Friday afternoon to call off a strike.

“This Company disrespected the process, bargained illegally and most of all, disrespected the finest Aerospace workers anywhere on the planet by failing to meet your expectations,” wrote Tom Wroblewski, district Machinists’ president, in a message to union members posted online Friday.

Wroblewski thanked the mediator but said despite meeting late into the night and throughout Friday, Boeing failed to “address our issues.”

The Machinists’ leaders had urged members to reject Boeing’s contract offer when they voted on Wednesday. The union has said Boeing’s contract did not live up to members’ expectations in regards to wages, health care, job security and paid time off.

Boeing had offered an 11 percent wage increase over three years as well as a $2,500 signing bonus. Machinists also would have received a lump sum payment in the first year equal to 6 percent of their salary, including overtime, or a minimum of $2,500.

But the union said the contract contained several takeaways and shifted costs around.

“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. Unfortunately the differences were too great to close,” said Scott Carson, president and CEO of Boeing Commercial Airplanes, in a statement Friday.

Carson also had sent a memo to employees after the Machinists’ vote Wednesday night. He described Boeing’s offer as “outstanding.” Carson emphasized the wide-ranging impact a labor strike at Boeing would have.

“Our customers are obviously going to be affected. …Our suppliers, too, will feel the impact immediately,” Carson wrote.

“And there’s no question about the negative economic effect on our local communities,” Carson continued.

During the work stoppage, Boeing will support its customers and their airplanes in service, the company said in statement. Boeing will continue delivering airplanes that were completed prior to the strike, and will continue providing customers with spare parts. Boeing does not intend to assemble airplanes during the strike.

Analysts have estimated that Boeing could feel the impact of a labor strike to the tune of $100 million daily.

Local labor economist Donna Thompson predicted that a month-long Machinists’ strike would take about $100 million in paychecks out of Snohomish County’s economy. Although the Machinists went on strike in 2005 for 28 days, it is unknown how long the strike could go on.

Gov. Chris Gregoire, who had facilitated talks with the mediator, called the breakdown in talks between Boeing and the Machinists “unfortunate,” in a statement.

“I urge both parties to continue working on a resolution and settle the strike as quickly as possible,” she said.

Industry observers have said that Boeing will try to keep the strike short, considering the company has a record backlog of commercial jet orders. Boeing also needs its Machinists in place to get its delayed 787 Dreamliner on track.

“If this Company wants to talk, they have my number, they can reach me on the picket line,” Wroblewski wrote in his message to Machinists.