* SSEC -0.9 pct, CSI300 -0.6 pct, HSI -0.1 pct
* HK->Shanghai Connect daily quota used 2.7 pct, Shanghai->HK daily quota used 0.4 pct
* FTSE China A50 +0.0 pct, BNY Mellon ADR China Select Index
SHANGHAI, June 15 (Reuters) - China stocks extended losses on Friday, with the benchmark Shanghai index plumbing a 20-month low, as investors worried rising trade tensions with the United State could add pressure to the country's economic growth.
** The CSI300 index fell 0.6 percent to 3,749.07 points at the end of the morning session, while the Shanghai Composite Index hit its lowest since September 2016 before sliding 0.9 percent to 3,016.57 points.
** Both indexes looked set for their third session of losses in a row.
** More than 40 stocks tumbled the maximum allowed 10 percent, led by tech firms, in particular small-cap companies.
** China's tech-heavy start-up board ChinextP dropped 1.9 percent to a four-month low.
** "There is a long-term correction in the valuations for those small-cap firms, as they are still over-valued without solid results," said Zhu Junchun, an analyst with Lianxun Securities.
** Investors were closely watching the development of China-U.S. trade spat.
** U.S. President Donald Trump has made up his mind to impose "pretty significant" tariffs and will unveil a list targeting $50 billion of Chinese goods on Friday, an administration official said. Beijing has warned that it was ready to respond.
** While it is not clear when Trump will activate the measures, rising Sino-U.S. trade tensions will put additional pressure on China's economy, which is starting to show signs of cooling under the weight of a multi-year crackdown on riskier lending.
** "Amid the continued weakness in the A-share market and external uncertainties, there are strong expectations that Beijing could roll out more supportive policies than just holding fire on rates, including reserve requirement ratio (RRR) cut and fiscal policies to bolster the real economy," Zhu said.
** In Hong Kong, the Hang Seng index dropped 0.1 percent, to 30,399.92 points, while the Hong Kong China Enterprises Index lost 0.4 percent, to 11,898.03.
** Around the region, MSCI's Asia ex-Japan stock index was weaker by 0.30 percent while Japan's Nikkei index was up 0.38 percent.
** The yuan was quoted at 6.4146 per U.S. dollar, 0.22 percent weaker than the previous close of 6.4005.
** The largest percentage gainers in the main Shanghai Composite index were Zhengzhou Coal Industry & Electric Power Co Ltd up 7.99 percent, followed by Kingswood Enterprise Co Ltd gaining 6.61 percent and Shanxi Coal International Energy Group Co Ltd up by 5.91 percent.
** The largest percentage losses in the Shanghai index were Shanghai Chuangli Group Co Ltd down 10.06 percent, followed by NINGBO BIRD Co Ltd losing 10.04 percent and Shanghai Greencourt Investment Group Co Ltd down by 10.04 percent.
** The top gainers among H-shares were Air China Ltd up 2.03 percent, followed by Shenzhou International Group Holdings Ltd gaining 1.64 percent and China Vanke Co Ltd up by 1.63 percent.
** The three biggest H-shares percentage decliners were Great Wall Motor Co Ltd which has fallen 3.31 percent, Huaneng Power International Inc which has lost 3.0 percent and CITIC Securities Co Ltd down by 2.8 percent.
** About 8.58 billion shares have traded so far on the Shanghai exchange, roughly 65.9 percent of the market's 30-day moving average of 13.03 billion shares a day. The volume traded was 11.55 billion as of the last full trading day.
** As of 04:05 GMT, China's A-shares were trading at a premium of 20.52 percent over the Hong Kong-listed H-shares.
** The Shanghai stock index is below its 50-day moving average and below its 200-day moving average.
** The price-to-earnings ratio of the Shanghai index was 13.12 as of the last full trading day while the dividend yield was 2.6 percent.
** So far this week, the market capitalisation of the Shanghai stock index has fallen by -0.63 percent to 31.54 trillion yuan.
(Reporting by Luoyan Liu and John Ruwitch; Editing by Simon Cameron-Moore)