Dec 17 (Reuters) - Canada"s main stock index fell on Friday, extending losses for a second session as energy stocks weighed, with concerns around surging Omicron cases around the world keeping sentiment in check. At 9:40 a.m. ET (14:40 GMT), the Toronto Stock Exchange"s S&P/TSX composite index (.GSPTSE) was down 119.79 points, or 0.58%, at 20,619.99. The energy sector (.SPTTEN) dropped 1.7% as oil prices dipped on Friday, putting the market on track for a weekly loss, as surging cases of the Omicron coronavirus variant raised fears new curbs may hit fuel demand. The rapid spread of Omicron coronavirus cases in the U.S. has forced some companies to pause plans to get workers back into office, while the number of cases in countries including Denmark, South Africa and Britain has been doubling every two days. read more "With the impact of the Omicron Wave on the world economy still uncertain, and economic news winding down heading into two holiday-shortened weeks, investors continue to retrench, with capital leaving risk markets and moving toward defensive havens," said Colin Cieszynski, chief market strategist at SIA Wealth Management. Limiting further losses were the materials sector (.GSPTTMT), which includes precious and base metals miners and fertilizer companies, added 0.7% as gold rose and was en route to its first weekly gain in five buoyed by a subdued dollar. The benchmark equity index was on track for recording weekly losses as concerns around rising Omicron cases, weakness in commodities and hawkish central banks rattled investors appetite for riskier assets. HIGHLIGHTS Converge Technology Solutions Corp (CTS.TO) and Bombardier Inc were the biggest decliners on the index. The TSX posted two new 52-week highs and six new lows. Across all Canadian issues there were seven new 52-week highs and 20 new lows, with total volume of 85.06 million shares.