SHANGHAI, Oct 28 (Reuters) - China"s yuan eased on Thursday, briefly weakening past a key threshold to its lowest in a week, dragged by stronger dollar demand, while investors anxiously awaited major central bank meetings for any clues on policy tightening in other economies. Higher dollar demand from corporates and banks" proprietary accounts was driven by renewed U.S.-China tensions, month-end dollar buying and continued worries about the financial health of Chinese property developers, currency traders said. Prior to market opening, the People"s Bank of China (PBOC) set the midpoint rate at 6.3957 per dollar, 101 pips or weaker than the previous fix of 6.3856. In the spot market, the onshore yuan opened at 6.3985 per dollar and quickly touched a low of 6.4052, the weakest level since Oct. 20. By midday, the spot yuan was changing hands at 6.3975, 60 pips softer than the previous late session close. Traders said market sentiment was hurt since late Wednesday afternoon after Reuters reported that some Chinese property developers had proposed extending their offshore bond maturities or undertaking a debt restructuring in a meeting with regulators, citing sources. The news suggested to some investors that those troubled developers barely had enough money to pay back their debt, a trader at a foreign bank said. The yuan was also hit by fresh signs of U.S.-China tensions. President Joe Biden told Southeast Asian nations the United States would stand with them in defending freedom of the seas and democracy and called China"s actions towards Taiwan "coercive" and a threat to peace and stability. Some traders expected the yuan to find support around the psychologically important 6.4 per dollar as Chinese government bonds are set to be included in the FTSE Russell flagship World Government Bond Index (WGBI) on Oct. 29, which should attract more foreign capital inflows and support the yuan. Meanwhile, the market was focused on the policy meetings of the Bank of Japan and the European Central Bank this week, as the monetary policy divergence between China and other major economies could affect fund flows and currency markets, traders added. In China, the central bank has been injecting 200 billion yuan into the financial system daily through open market operations this week, resulting a in a net injection of 60 billion yuan so far this month, compared with a net drain of 260 billion yuan in October 2020. "Hopes for PBOC"s board reserve requirement ratio (RRR) cut have been diminishing...," said Ken Cheung, chief Asian FX strategist at Mizuho Bank in Hong Kong. "It appears that the PBOC can manage to contain the fallouts from the Evergrande crisis and a broad RRR cut is no longer needed to keep liquidity condition reasonably ample given the support from more flexible reverse repo operations." By midday, the broad dollar index stood at 93.839, while the offshore yuan was trading at 6.3959 per dollar. The yuan market at 0401 GMT: ONSHORE SPOT: Item Current Previous Change PBOC midpoint 6.3957 6.3856 -0.16% Spot yuan 6.3975 6.3915 -0.09% Divergence from 0.03% midpoint* Spot change YTD 2.04% Spot change since 2005 29.37% revaluation Key indexes: Item Current Previous Change Thomson 100.31 100.47 -0.2 Reuters/HKEX CNH index Dollar index 93.839 93.898 -0.1 *Divergence of the dollar/yuan exchange rate. Negative number indicates that spot yuan is trading stronger than the midpoint. The People"s Bank of China (PBOC) allows the exchange rate to rise or fall 2% from official midpoint rate it sets each morning. OFFSHORE CNH MARKET Instrument Current Difference from onshore Offshore spot yuan 6.3959 0.03% * Offshore 6.5766 -2.75% non-deliverable forwards ** *Premium for offshore spot over onshore **Figure reflects difference from PBOC"s official midpoint, since non-deliverable forwards are settled against the midpoint. . (Reporting by Winni Zhou and Andrew Galbraith; Editing by Ana Nicolaci da Costa)