May 7 (Reuters) - Canada's main stock index fell on Tuesday, as worries about a deterioration in trade negotiations between the United States and China made investors wary of riskier assets.
* At 9:47 a.m. ET, the Toronto Stock Exchange's S&P/TSX composite index was down 109.13 points, or 0.66 percent, at 16,384.33, extending its decline from the previous day when U.S. President Donald Trump vowed to double down tariffs on Chinese goods.
* U.S. Trade Representative Robert Lighthizer said on Monday Beijing had reneged on commitments it had made previously that would have changed the agreement substantially.
* Chinese Vice Premier Liu He is expected to be in Washington on Thursday and Friday for further talks.
* Nine of the 11 major sectors were lower, led by a 2.04 percent drop in the energy sector. Oil prices took another beating amid concerns over global growth.
* The materials sector, which includes precious and base metals miners and fertilizer companies, lost 1.3 percent as copper prices headed toward 2-1/2 month lows.
* Iamgold Corp fell 10.3 percent, the most on the TSX, after the gold miner reported quarterly revenue below estimates. The second biggest decliner was Hudbay Minerals Inc , down about 10 percent after results.
* The largest percentage gainers on the TSX were Kirkland Lake Gold Ltd, which rose 4.8 percent and WestJet Airlines Ltd that jumped 3.3 percent after their results.
* The most heavily traded shares by volume were Enbridge Inc , Hanwei Energy Services and Harte Gold Corp .
* The TSX posted three new 52-week highs and five new lows.
* On the TSX, 64 issues were higher, while 168 issues declined for a 2.63-to-1 ratio to the downside, with 24.14 million shares traded.
* Across all Canadian issues there were seven new 52-week highs and eight new lows, with total volume of 39.93 million shares. (Reporting by Sruthi Shankar in Bengaluru; Editing by Arun Koyyur)