(Updates prices, sectors) July 8 (Reuters) - Canada’s main stock index fell on Thursday, set for its biggest drop in over four months, weighed by a 2.4% drop in energy stocks as crude prices extended losses on supply uncertainty. * The energy sector dropped 2.4% as crude prices fell on fears the current output agreement could be abandoned after the collapse in talks among OPEC+ members. * Meanwhile, the financials sector and material stocks slipped 1.5% and 0.9%, respectively, adding to the downbeat mood. * At 9:38 a.m. ET (13:38 GMT), the Toronto Stock Exchange’s S&P/TSX composite index was down 235.16 points, or 1.16%, at 20,055.44. * Uranium company Nexgen Energy Ltd fell 4.8%, the most on the TSX. The second biggest decliner was fashion retailer Aritzia Inc, down 4.7%. * On the TSX, 16 issues were higher, while 210 issues declined for a 13.13-to-1 ratio to the downside, with 15.56 million shares traded. * The largest percentage gainers on the TSX were Parex Resources Inc, which jumped 2.4% after multiple brokerages raised their price targets for the oil producer’s stock, and railroad operator Canadian National Railway Co , which rose 2.1%. * The most heavily traded shares by volume were Bombardier Inc, Headwater Exploration Inc and Crescent Point Energy Corp. * The TSX posted no new 52-week highs and no new lows. * Across all Canadian issues there were nine new 52-week highs and eight new lows, with total volume of 35.49 million shares. (Reporting by Amal S in Bengaluru; Editing by Krishna Chandra Eluri) Our Standards: The Thomson Reuters Trust Principles.