OTTAWA, Jan 21 (Reuters) - Canadian retail sales most likely fell by 2.1% in December as authorities imposed restrictions to fight the Omicron variant of the coronavirus and retailers faced challenges, Statistics Canada predicted on Friday. Statscan also said retail sales rose 0.7% in November, which was less than the 1.2% gain forecast by analysts. The flash estimate for December was based on responses from 50.6% of companies surveyed. The average response rate is 90.0%. Statscan also said some shoppers decided to pull forward their purchases to November to avoid shortages caused by endemic supply chain issues. Andrew Grantham, senior economist at CIBC Capital Markets, said the December dip was a little larger than he had expected. "Bricks-and-mortar retailers will have likely continued to struggle in January due to Omicron-related restrictions and staff shortages," he said in a note. This weakness, he suggested, might "tip the scales slightly" in terms of persuading the Bank of Canada to hold steady when it makes a rate announcement on Jan 26. Money markets see about a 70% chance that the central bank will lift its key overnight rate from the current record low 0.25%. {BOCWATCH] The bank has previously said it could raise rates as early as soon as April. Stephen Brown, senior Canada economist at Capital Economics, said the December decrease in sales was likely to be more than 2.1%, given the rapid spread of Omicron that month. November"s gain was fueled by higher sales at gasoline stations, and at building materials and gardening equipment and supplies dealers. Sales rose in six of 11 subsectors, representing 63.8% of retail trade. In volume terms, retail sales edged up 0.2%. The Canadian dollar was trading 0.1% lower at 1.2520 to the greenback, or 79.87 U.S. cents.