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BEIJING—Foreign companies have been teaming up with Chinese ones for years to gain access to the giant Chinese market. Now some of the world's biggest companies are taking a risky but potentially rewarding second step—folding pieces of their world-wide operations into partnerships with Chinese companies to do business around the globe.

General Electric Co. is finalizing plans for a 50-50 joint venture with a Chinese military-jet maker to produce avionics, the electronic brains of aircraft. The deal with Aviation Industry Corp. of China would give GE access to a Chinese government project aimed at challenging Boeing Co. and Airbus in the civilian-aircraft market.

General Motors Co. established a joint venture this year with SAIC Motor Corp. , its longtime partner in China, to produce and sell their no-frills Wuling-brand microvans in India, and eventually in Southeast Asia and other emerging markets as well.

The two deals show China Inc.'s growing international ambitions, as well as its increasing leverage over foreign partners. To make the deal happen, GE Chief Executive Jeffrey Immelt agreed to fold into the venture some of his company's global business in nonmilitary avionics. GM, in its deal, contributed technology, its manufacturing facilities in India and use of its Chevrolet brand name in that market.