Seattle ? Negotiators for Boeing’s largest union were headed back to the Northwest on Saturday after ending their talks with federal mediators in Washington, D.C.

The Machinists plan a second vote on Boeing’s “best and final” offer from Aug. 27, but no date for that second balloting had been set.

Union leaders are again recommending rejection of the pact, which means the labor dispute is right back where it was Aug. 29, when the Federal Mediation and Conciliation Service stepped in as Machinists voted the first time.

The Machinists represent 25,000 Boeing production workers in Washington state, Portland, Ore., and Wichita, Kan., who have been working without a contract since the previous agreement expired Sept. 1.

The vote will be scheduled “as soon as we can get it arranged,” said Connie Kelliher, spokeswoman for District 751, the Machinists’ biggest lodge here.

Kelliher said union leaders needed to choose a date, then print and mail voter eligibility cards. She said she did not know if any general membership meetings had been scheduled.

Boeing officials are more than ready for a vote on their proposed three-year contract.

“It’s not fair that they keep delaying,” company spokes-man Chuck Cadena said Saturday. “A revote should happen in a timely manner, and it should be fair.”

Boeing refused the mediation service’s Aug. 29 invitation to return to the table, saying the company had nothing to add.

“We were ready for that offer to go to a vote on Aug. 27,” Cadena said Saturday. “We’re ready for that offer to go to a vote today.”

The results of the Machinists vote Aug. 29 were sealed, uncounted, and union leaders met with federal mediators in Washington, D.C. Boeing officials refused to meet with the Machinists but met with the mediator Wednesday to explain their offer.

After 2 1/2 days of talks without Boeing, the union officials decided to return home.

The company’s three-year contract offer provides an 8 percent ratification bonus, and raises of 2 percent and 2.5 percent in the second and third years.

It also includes changes in health-care costs for many employees.

The contract increases pension payments by 20 percent in the contract’s third year, paying retirees $60 a month per year of service far less than the $120 a month per year sought by the union.

Boeing refused a union proposal to link the level of employment to airplane deliveries or other business benchmarks, a critical issue for the union, whose membership has dropped by 25 percent over the past year because of layoffs.