HONG KONG, April 3 (Reuters) - An Andy Warhol portrait of former Chinese leader Chairman Mao Zedong has sold for $12.6 million at a Hong Kong auction, less than the $15 million it was expected to fetch.

The painting was sold to a private Asian collector at Sotheby's evening sale on Sunday.

Warhol began his series of silk-screen portraits of Mao in 1972 when ties between then Cold War foes China and the United States began to thaw after U.S. President Richard Nixon's historic trip to Beijing.

(Reporting by Reuters Television; Editing by Michael Perry)