Canada's main stock index fell on Tuesday, dragged by weakness in the materials sector, while concerns about potential roadblocks to US stimulus weighed on investor sentiment.

The materials sector, which includes precious and base metals miners and fertilizer companies, lost 0.5%.

Investors are watching the progress in the US stimulus talks as lawmakers locked horns over the size of a pandemic relief package outlined by the new US president Joe Biden.

At 9:45 a.m. ET (14:45 GMT), the Toronto Stock Exchange's S&P/TSX composite index was down 20.27 points, or 0.11%, at 17,885.75.

Aurinia Pharmaceuticals Inc fell 4.5%, the most on the TSX, after brokerage Mackie Research downgraded the rating of the biotech firm and the second biggest decliner was Yamana Gold Inc, down 4.1% after the miner released its preliminary fourth quarter and 2020 production results.

The energy sector climbed 0.5% as US crude prices were up 0.4% a barrel, while Brent crude added 0.6%.

The financials sector slipped 0.1%, while the industrials sector rose 0.4%.

On the TSX, 106 issues were higher, while 108 issues declined for a 1.02-to-1 ratio to the downside, with 21.54 million shares traded.

The largest percentage gainers on the TSX were TFI International Inc, which jumped 12.9% after multiple brokerages raised the price target of the logistics services provider's stock.

Its gains were followed by Canopy Growth Corp, which rose 7.5% after pot producer launched a new line of Cannabidiol (CBD) products for pets.

The most heavily traded shares by volume were Blackberry Limited, Supreme Cannabis Company Inc, and Bombardier Inc.

The TSX posted 13 new 52-week highs and no new lows.

Across all Canadian issues there were 105 new 52-week highs and nine new lows, with total volume of 47.33 million shares.