SHANGHAI, Jan 15 (Reuters) - China’s blue-chip stocks eased on Friday, snapping a four-week winning streak, as worries over Sino-U.S. tensions and a surge in COVID-19 cases weighed on investor sentiment. ** The blue-chip CSI300 index fell 0.2% to 5,458.08, shedding 0.7% for the week. ** The Shanghai Composite Index ended flat at 3,566.38, down 0.1% for the week - also snapping four straight weekly gains. ** The Trump administration in its waning days took another swipe at China and its biggest firms on Thursday, imposing sanctions on officials and companies for alleged misdeeds in the South China Sea and an investment ban on nine more firms. ** The moves will further increase tensions with China, Washington’s strategic rival in Asia, days before President-elect Joe Biden takes office on Wednesday. ** Adding to the pressure was the resurgence of COVID-9 cases in the world’s second-largest economy. ** China reported the highest number of daily COVID-19 cases in more than 10 months, official data showed, due to a severe outbreak in the northeast that has put more than 28 million people under lockdown. ** Leading the decline, the CSI300 consumer staples index dropped 2.1%, while the CSI liquor index lost 3.4%. For the week, the CSI300 consumer staples index fell 5.6% and the CSI liquor index slumped 8%. ** China Fortune Securities said in a report that market participants would need time and earnings from some leading firms to digest their lofty valuations, noting that the overall price-to-earnings ratio of liquor makers had doubled to 66 from the end of 2010. ** Bucking the broader weakness, banking shares staged a strong rally, as more banks forecast upbeat earnings for 2020 despite the coronavirus outbreak. (Reporting by Shanghai Newsroom; Editing by Subhranshu Sahu)