* Sunac may buy as much as 30 pct for up to $645 million
* Move would boost its position in luxury real estate market
* Consolidation expected in China's property sector this year (Adds details about the companies, sector)
By Clare Jim
HONG KONG, May 16 (Reuters) - Sunac China Holdings Limited is in talks to buy up to 30 percent of fellow property developer Greentown China Holding Ltd, a move that would boost its position in the country's luxury real estate market.
The deal would be worth as much as HK$5 billion ($645 million) based on Greentown's last closing price, and it would make Sunac the largest shareholder in Greentown, which is based in the eastern city of Hangzhou.
China's overheated property market is facing tight liquidity and developers and industry observers expect consolidation in the sector this year.
Greentown said that while the two companies were in discussions, it had not yet received a formal offer. It is China's eighth largest developer by sales so far this year, while Sunac is the ninth.
Shares of Greentown rose 6 percent as of 0309 GMT, while shares of Sunac shed 5.3 percent. The Hang Seng Index declined 0.7 percent.
Suffering from financial woes two years ago, Greentown sold some projects in China to Sunac for HK$3.37 billion. It also sold shares and perpetual subordinated convertible securities to Hong Kong's Wharf Holdings Ltd for HK$5.1 billion. Wharf now holds 24.3 percent of Greentown. ($1 = 7.7519 Hong Kong Dollars) (Reporting by Clare Jim; Editing by Edwina Gibbs)