* SSEC -1.3%, CSI300 -1.6% * Tensions between China and major western economies weigh * China administers 82.85 mln doses of COVID-19 vaccines, as of Tues BEIJING/SHANGHAI, March 24 (Reuters) - Chinese shares fell on Wednesday to their lowest close in three months as risk appetite soured on concerns of policy tightening and escalating tensions between China and major western economies. ** At the close, The blue-chip CSI300 index was down 1.61% at 4,928.69, the lowest close since Dec. 11, while the Shanghai Composite index fell 1.3% to 3,367.06, the weakest close since Dec. 24. ** Leading the decline, the CSI300 resource index slumped 4.2%, while the CSI300 transport index lost 4%. The financial sector sub-index was lower by 1.2%, while the real estate index fell 2.24%. ** The smaller Shenzhen index ended down 1.41% and the start-up board ChiNext Composite index was weaker by 1.25%. ** Chinese shares have been fluctuating at the bottom for a while due to various of external factors but a rebound should come soon as companies are to report strong first-quarter earnings, said Zhang Yanbing, an analyst with Zheshang Securities. ** China’s National Health Commission said that a total of 82.85 million doses of COVID-19 vaccines had been administered, as of Tuesday. ** Around the region, MSCI’s Asia ex-Japan stock index was weaker by 1.21%, while Japan’s Nikkei index closed down 2.04%. ** At 07:14 GMT, the yuan was quoted at 6.5237 per U.S. dollar, 0.12% weaker than the previous close of 6.516. ** So far this year, the Shanghai stock index is down 3.1% and the CSI300 has fallen 5.4%, while China’s H-share index listed in Hong Kong is up 0.9%. Shanghai stocks have declined 4.05% this month. (Reporting by Shanghai Newsroom; Editing by Subhranshu Sahu)