Boeing Co. is expected to extend by a decade its contract with a Chinese aircraft maker to produce horizontal stabilizers for Boeing's 737 jet, part of a charm offensive in one of its most important markets.

Yin Xiufeng, an official with Commercial Aircraft Corp. of China, or Comac, which owns the contractor, Shanghai Aircraft Manufacturing Co., said the Shanghai company and Boeing are expected on Wednesday in Beijing to sign a 10-year contract extension for the stabilizer supply contract. Exact terms of the contract extension weren't immediately clear.

Chicago-based Boeing is expected to announce the extension at Aviation Expo, an exhibition that kicks off in Beijing Wednesday. Boeing China President Marc Allen and Ihssane Mounir, a senior sales executive for Boeing's commercial airliner unit, are due to hold a press conference at the exhibition.

Wang Yukui, a Beijing-based spokesman for Boeing, declined to comment.

Boeing in recent years has shifted production of some components outside North America. The moves help drive down manufacturing costs and can strengthen Boeing's position in markets like China that are trying to nurture commercial aerospace industries and where the government influences aircraft-purchase decisions.

Boeing recently redesigned the 737 to carry new engines to boost fuel efficiency and lower operating costs, but it hasn't won any orders in mainland China yet for the plane, dubbed the 737 MAX.

Shanghai Aircraft Manufacturing has been producing horizontal stabilizers for the 737 since the late 1990s, Comac's Mr. Yin said. Since 1999, the company has delivered more than 2,000 horizontal stabilizers for the airplane, he said.

Boeing on Wednesday is also expected to provide an update on its business in China. A person close to Boeing said the company is unlikely to announce new orders for its passenger aircraft from mainland China airlines and other customers.

Boeing currently has orders for a total of 60 Boeing 787 Dreamliner jets from China Southern Airlines Co. and other mainland China customers.

Earlier this month, Boeing raised its 20-year forecast for China's spending on commercial aircraft by 25%, citing Chinese airlines' planned international expansion in what the company expects will become the world's second-biggest aircraft market, after the U.S.

In that forecast, Boeing said it expects Chinese carriers and others to spend US$600 billion for 5,000 new commercial airplanes from Boeing, Airbus and other manufacturers. Boeing last year estimated that China would spend US$480 billion on 4,330 planes over the next 20 years.