The major order, announced as Chinese President Xi Jinping toured Boeing's Everett, Washington, factory, includes some planes that were previously ordered but for which the buyers had not yet been identified. Boeing declined to say how many of the planes had been previously ordered, and how that would affect the actual value of the deal.

Earlier on Wednesday, China's ICBC Financial Leasing Co, a unit of the Industrial and Commercial Bank of China 601398.SS, separately confirmed it will buy 30 of Boeing's 737-800 jets, worth $2.88 billion at list prices.

Boeing also was due to announce later in the day an agreement to build a 737 completion center in China that would finish and deliver 737s built at Boeing's factory in Renton, Washington.

Machinist union members say they stand to lose work to China and were due to protest on Wednesday. Boeing said on Tuesday it doesn't expect to lay off or reduce staff related to the 737 because of the new factory in China.

Boeing is battling with rival Airbus Group for dominance of Chinese market, which Boeing says will need $1 trillion worth of new planes over the next two decades.

Airbus supplied 6 percent of mainland China's aircraft in 1995, but in 2008 the European plane maker put an assembly plant in China to make its A320 aircraft, which competes with Boeing's 737. Today, Airbus planes account for about half the in-service fleet. Last week Airbus opened an A320 factory in Alabama, its first on U.S. soil.

Boeing's China venture would be less ambitious. Planes built at Boeing's Renton, Washington, factory would be flown to China for interior installation, painting and delivery to customers.

During the factory tour, Xi walked through a 787 Dreamliner, touching the blue seats and admiring the space between them. Boeing Commercial Airplanes Chief Executive Ray Conner demonstrated the dimmable window function on the high-tech 787.