SEATTLE — Unless Boeing Co. can win a long-term contract that bars strikes by its largest union, the aerospace company will build a second production line for its new 787 jetliner outside of Washington state, members of the state's congressional delegation say.

The machinists union, which represents production workers at Boeing, has struck the company four times over the past 20 years, most recently last fall for two months.

"The whole thing comes down to, can they get a long-term agreement with the union, with a no-strike clause?" U.S. Rep. Norm Dicks, D-Wash., said in an interview with The Seattle Times on Tuesday. He added, "I think if they get this agreement, they would stay."

In a separate interview with the newspaper, Gov. Chris Gregoire said Boeing Commercial Airplanes CEO Scott Carson also told her recently the company wants a long-term, no-strike agreement with the machinists union.

Gregoire said Carson told her Boeing probably will decide on the location of a second 787 production line this fall, although he did not specifically link that decision and a no-strike agreement as an ultimatum.

Machinists union District President Tom Wroblewski balked at the idea of setting aside the union's strike weapon.

"Take away our only power?" Wroblewski asked rhetorically. "I can't see ever taking our power away."

North Charleston, where major components of the 787 already are made, will most likely be a contender for that line, a Boeing executive told The Post and Courier this week.

On Tuesday, the Chicago-based aerospace giant said it would pay $580 million for the Vought Aircraft Industries plant at Charleston International Airport, where Vought makes aft-fuselage sections for the long-delayed 787.

Deliveries of the 787 have been postponed by nearly two years, partly because of problems with components made by suppliers, including Vought, and work that suppliers didn't complete. Those problems are expected to cost Boeing billions of dollars in added expenses and penalties.

Boeing is using suppliers from around the world to build large sections of the plane that are later assembled at the company's commercial aircraft plant in Everett, north of Seattle. Boeing has booked orders for a record 850 of the planes, though some 60 orders have been canceled so far this year.

Dicks, the third-ranking member of the House Appropriations Committee, has long been an aggressive Boeing supporter. He told The Times the labor ultimatum was laid out for him and other members of Washington's congressional delegation by "high-ranking people" at Boeing whom he declined to name.

Dicks also said that at a March meeting with Boeing CEO Jim McNerney, arranged by Gregoire and held in the Washington, D.C., office of Sen. Patty Murray, D-Wash., "McNerney was very candid."

"The message was that we need to get a resolution of this (strike) problem. We can't live with this," Dicks said.

He said Sen. Maria Cantwell, D-Wash., and most of Washington's U.S. representatives were present, as McNerney described how Boeing plans a detailed assessment of where to put a second 787 assembly line in an open competition, with Everett as only one option.

Boeing spokesman Jim Proulx said the company "can't comment on any conversations our senior executives may or may not have with government officials."

The International Association of Machinists and Aerospace Workers' current contract with Boeing expires in 2012.

Gregoire said that before Boeing decides on where to place a second 787 line, she plans to go to company headquarters in Chicago and make the case for the Puget Sound region before Boeing's board.

Gregoire said a no-strike agreement is an ambitious goal for Boeing, and is something that cannot be achieved through legislation. Dicks said any such agreement would have to involve some kind of binding independent arbitration of disputes between Boeing and the machinists.

Wroblewski said there have not yet been any extensive discussions on the subject.

"If we were to have these discussions, the company would have to come through with something, ... guaranteed employment of some sort," he said. "The trade-offs would be huge."

Vought production workers in North Charleston are represented by the machinists union. Boeing said it plans to negotiate a new labor contract with the union as part of its purchase of the local plant.