NEW YORK (Reuters) - United Airlines said on Tuesday it had expanded its code-sharing cooperation with Air China Ltd to cover another 22 routes in the Chinese and U.S. markets, intensifying competition among U.S. carriers for travellers to Asia.

Effective immediately, United will code-share on 10 additional domestic routes in China on Air China-operated flights, while Air China will code-share on 12 more U.S. domestic routes on United-operated flights.

With the latest arrangement, the airlines will now code-share on 110 routes. (http://prn.to/1FSd4Mr)

Among U.S. airlines, United Airlines currently serves the greatest number of destinations in the Asia-Pacific region, including Australia and New Zealand, with 31 destinations, followed by Delta Air Lines Inc, with 17.

The numbers do not include code-share arrangements.