SHANGHAI, Feb 18 (Reuters) - China’s blue-chip index ended lower after scaling an all-time high on Thursday, the first trading session after a week-long Lunar New Year holiday, on worries over policy tightening and lofty valuations. ** The blue-chip CSI300 index climbed as much as 2.1% to an all-time high of 5,930.9, before closing down 0.7% at 5,768.38, while the Shanghai Composite Index rose 0.6% to 3,675.36. ** The tech-heavy start-up board ChiNext fell 2.7%, while Shanghai’s STAR50 index shed 0.5%. ** Among sectors, the CSI300 consumer staples index and the CSI300 healthcare index fell the most, dropping 3.8% and 4.3%, respectively. ** Analysts and traders said the market’s focus is now on liquidity conditions, which could impact risk appetite. ** The People’s Bank of China injected another 20 billion yuan on Thursday via reverse repos, while 280 billion yuan worth of a similar liquidity tool was set to expire on the same day. ** “We believe that several recent developments during the Chinese New Year have made monetary policy tightening more likely in the coming months,” Zhiwei Zhang, chief economist at Pinpoint Asset Management, noted in a report. ** Zhang said the developments included a potential larger-than-expected U.S. fiscal stimulus, the success in the fight against the pandemic, and positive high-frequency data on economic activities during the holiday. ** Worries over valuations also contributed to the fall in high-flying sectors, including consumer, healthcare and new energy firms. ** “Institutional investors had already began to cut exposure, after stellar gains that had pushed valuations of some sectors to lofty levels,” said Hu Yunlong, chief investment officer at Beijing Kaixing Asset Management Company. ** “For now, investors tend to rebalance their allocations and shift towards sectors with low valuations, like banking and securities firms.” ** Bucking the broad weakness, the CSI300 financials index gained 2%, while the CSI300 energy index jumped 5.8% on oil price gains. (Reporting by Luoyan Liu and Brenda Goh; Editing by Subhranshu Sahu)