Airbus Group NV won a pledge from China Aircraft Leasing Group Holdings Ltd for the purchase of 100 planes valued at $10.2 billion as the Chinese lessor seeks to build a portfolio to power expansion in the region.

The order is for 100 single-aisle A320 planes, a combination of existing models and future ones with new engines, the Tianjin-based company said in a statement to the Hong Kong stock exchange on Thursday. A formal agreement may be signed before the end of the month, it said.

Leasing companies are boosting their fleets and expanding across Asia as the region is set to overtake the US as the world's largest plane market, spurred by demand from China, India and Southeast Asia.

Last month, China said it will encourage its lessors to look for opportunities overseas. Hong Kong billionaire Li Ka-shing's Cheung Kong Holdings Ltd has submitted a preliminary proposal for some planes of Awas Aviation Capital Ltd.

Thursday's agreement comes less than a month after Airbus won a commitment for 250 planes valued at $26 billion at list price from Indian budget carrier IndiGo. Carriers in China, India and other Asian countries are buying more planes as economic growth lifts demand for air travel.

CALC in July became the first plane lessor in the region to go public, and has been seeking to expand throughout Asia. In August it signed an agreement with India's state-owned carrier Air India Ltd to lease five Airbus Group NV A320s starting next year. That was the company's first leasing pact with a non-Chinese carrier.

Last month, Airbus also won an agreement from China for 70 A320 single-aisle family planes valued at $7 billion. China is poised to displace the US as the world's largest plane market in two decades, according to the European planemaker.