SHANGHAI, Dec 3 (Reuters) - China stocks edged lower on Thursday after the U.S. House of Representatives passed a bill that threatened to delist Chinese companies off U.S. stock exchanges, a move likely to further ratchet up tensions between Washington and Beijing.

** Measures taking a harder line on Chinese business and trade practices generally pass U.S. Congress with large margins. Both Democrats and Donald Trump's fellow Republicans echo the president's hard line against Beijing, which became fiercer this year as Trump blamed China for the coronavirus ravaging the United States.

** At the midday break, the Shanghai Composite index was down 0.09% at 3,446.19 points, while China's blue-chip CSI300 index slipped 0.11%. ** Chinese H-shares listed in Hong Kong fell 0.07% to 10,566.52, while the Hang Seng Index was up 0.56% at 26,682.16. ** The smaller Shenzhen index was up 0.17%, the start-up board ChiNext Composite index was higher by 1.25% and Shanghai's tech-focused STAR50 index was up 0.56%.

** Pharmaceuticals outperformed the market, with vaccine-related stocks limiting losses in the index, after the Institute of Microbiology at the Chinese Academy of Sciences said it worked with China's Chongqing Zhifei to carry out a phase III trial of a coronavirus vaccine in China's Hunan province in November. The company was up 7% by midday, while the healthcare sub-index rose 3.11%.

** Around the region, MSCI's Asia ex-Japan stock index was firmer by 0.27% while Japan's Nikkei index was up 0.01%.

** The largest percentage losses in the Shanghai index were Dalian Sunasia Tourism Holding Co Ltd, down 10.009%, followed by Changzhou Langbo Sealing Technologies Co Ltd , losing 9.99% and Xilinmen Furniture Co Ltd , down by 8.858%.

** So far this year, the Shanghai stock index is up 13% and the CSI300 climbed 23.6%, while China's H-share index listed in Hong Kong dropped 5.4%. Shanghai stocks advanced 1.6% so far this month.

(Reporting by Winni Zhou and Andrew Galbraith, Editing by Sherry Jacob-Phillips)