* SSEC -0.1%, CSI300 -0.1%, HSI 0.5% * HK->Shanghai Connect daily quota used -1.4%, Shanghai->HK daily quota used 5.2% * FTSE China A50 -0.6% SHANGHAI, April 22 (Reuters) - China stocks slipped on Thursday, weighed by persistent worries over Sino-U.S. tensions, offsetting a series of upbeat corporate earnings in the first quarter. ** The CSI300 index fell 0.1%, to 5,092.72 points, at the end of the morning session, while the Shanghai Composite Index lost 0.1%, to 3,471.23 points. ** A bipartisan U.S. congressional push to counteract China picked up steam on Wednesday as a Senate committee overwhelmingly backed a bill pressing Beijing on human rights and economic competition and other lawmakers introduced a measure seeking billions for technology research. ** Also pressuring the market were concerns over liquidity. ** “Onshore mutual funds’ assets under management (AUM) and their positioning concentration has risen substantially since 2018, with the top-50 A-share favorites representing 45% of equity mutual funds’ AUM and 52% of Northbound holdings,” Goldman Sachs analysts, including Kinger Lau, said in report. ** “Further significant market weakness and redemption pressures could test the authorities’ downside risk tolerance especially in the lead-up to the Chinese Communist Party’s centenary celebration on July 1,” GS added. ** Though the stock market has been quite stable for the past weeks, Ken Cheung, chief Asian FX strategist at Mizuho Bank in Hong Kong said market sentiment stabilized on news that China considered supporting Huarong with central bank funds. ** The value of shares investors in China’s onshore stock markets have borrowed to sell short reached 151.9 billion yuan ($23.43 billion) on Wednesday, just a touch below a record high hit on Tuesday. ** The increase came after China allowed foreign investors to conduct margin trading and securities lending deals in the A-share market, who had long complained about a lack of hedging tools. ** “There are more abundant hedging tools now than before, and it’s easier to borrow equities to sell short thanks to increasingly more sources of such equities,” said Li Bingyang, chairman of private securities fund Hangzhou Zhuhangusong Capital. ** Li added short selling could help better price discovery in the market. ** In Hong Kong, the Hang Seng index added 0.5%, to 28,754.82 points, while the Hong Kong China Enterprises Index gained 0.4%, to 10,930.46. ($1 = 6.4842 Chinese yuan renminbi) (Reporting by Luoyan Liu and Andrew Galbraith; Editing by Shailesh Kuber)