HONG KONG/SHANGHAI, July 19 (Reuters) - China state-backed Greenland Holdings has defaulted on a dollar bond worth $432 million due to a missed amortization payment, sources with knowledge of the matter said on Wednesday.

The default adds to the debt woes plaguing the Chinese property sector as more liquidity troubles have emerged in the past few weeks despite policy support.

Once a key growth driver, the real estate sector is now a significant drag on the cooling economy, spilling over into everything from construction to flagging consumer confidence and retail sales.

Problems at state developers, in particular, could signal more defaults among private developers in the second half, as the debt crisis that unfolded in mid-2021 shows little signs of stabilizing.

Another state-backed developer, Sino-Ocean Group, has initially proposed to creditors to extend the principal repayment of a 2 billion yuan ($277.29 million) onshore bond due August 2 by one year, two sources with direct knowledge said on Wednesday.

Beijing-based Sino-Ocean is the second state developer to extend its onshore bond payment. The firm

suspended trading

in the bond in question from Tuesday because of ongoing repayment negotiations with creditors.

The market is watching whether it will be able to repay an offshore coupon due later this month.

For Shanghai-based Greenland, the first state-backed developer to extend debt payments last year, it has failed to make a payment for the 6.75% June 2024 bond with an outstanding $432 million.

HSBC, trustee for the bond, notified holders on July 14 of an event of default because the developer did not pay the 5% amortization worth 22.5 million on due day, and the non-payment continued for the next seven days, according to Debtwire, who first reported about the default.

Late last year, the developer extended the maturity of the bond in question by another one year and a series of other bonds by two years. It promised to pay 5% of the principal on the original maturity dates, together with interest.

Greenland said they are in active communications with various parties, without elaborating further.

Sino-Ocean said it will publish details in future statements.

Two sources said Sino-Ocean has proposed to pay only interest on the maturity date of the onshore bond in question, and then 5% of principal in four instalments each from Sept., and complete the remaining 75% after one year.

China Evergrande Group, the world's most indebted property developer, posted a combined loss of $81 billion in 2021 and 2022 and a rise in total liabilities in its

long overdue results

on Monday.

($1 = 7.2126 Chinese yuan renminbi) (Reporting by Clare Jim and Xie Yu in Hong Kong, Steven Bian in Shanghai, Shuyan Wang in Beijing; Editing by Kim Coghill)