SEATTLE - The national union chief who has forced a vote on a pension-freezing Boeing contract proposal once called those retirement plans sacred and derided alternatives as risky.

In statements during the past few years, Tom Buffenbarger has advised union members about the importance of protecting defined-benefit pensions. He also warned that the union shouldn't "fall prey to the trap that's been set elsewhere by other companies and other industries where we don't have pensions for new hires."

Boeing workers, predominantly in the Puget Sound area, are set to vote Friday on a proposal that would freeze existing pensions and deny fixed pensions to new employees.

Since union rejected an initial contract offer in November, a total of 22 states have submitted bids to secure work on Boeing's new 777X aircraft, including South Carolina, where the company assembles the 787 Dreamliner.

Boeing is vowing to produce the new 777X airplane in the Seattle region if the contract is approved.

Buffenbarger, president of the International Association of Machinists and Aerospace Workers, told members in a 2010 video message that he couldn't see the union allowing Boeing to put such a divide between generations of workers.

"Our union, the IAM, holds a pension plan as a sacred, sacred benefit," Buffenbarger said. "We do not give it up without a fight. We do not sacrifice the unborn on the altar of corporate profits."

Despite his message, union workers in St. Louis voted that year to move away from fixed pension plans.

In the Puget Sound, Buffenbarger has forced the upcoming contract vote despite the objection of local union leaders who believe the contract involves too many concessions, particularly because of its shift away from pensions at a time when Chicago-based Boeing is profitable.

In response to an interview request by the Associated Press, Buffenbarger issued a written statement that Boeing's latest proposal on pensions cannot be viewed in isolation.

The company has offered to build the 777X in the Puget Sound if the contract proposal is accepted and reaffirmed that work on the 737MAX would remain. Buffenbarger said those offers would mean tens of thousands of jobs for the area and decades of prosperity for union members and their families.

"The loss of this work would have a far greater impact on members' retirement security than the changes Boeing has proposed to the current defined benefit plan," Buffenbarger said in his statement. "Our primary responsibility as a union is to protect our members' jobs and to give them a say in the wages, benefits and survival of those jobs."

Jay Cronk, who is challenging Buffenbarger for the presidency of the union, said Buffenbarger has turned 180 degrees from his past support of pensions. Cronk said union training courses have always taught workers the importance of pension plans to ensure retirement stability.

"He has always taken that position up until now," Cronk said.

Cronk believes Buffenbarger is looking for a long-term contract to secure a steady stream of revenue for the union that wouldn't be disrupted by a possible strike in the coming years.