US crude prices were down 0.76 percent at $49.79 a barrel as ample global supplies countered strong demand and forecasts of another drop in US crude inventories.

The US dollar edged higher against a basket of major currencies.

On Monday it fell to its lowest since May 2016 following news that the White House's communications director was leaving the post after 10 days.

At 9:10 a.m. ET (1310 GMT), the Canadian dollar was trading nearly unchanged at C$1.2481 to the greenback, or 80.12 US cents.

The currency traded in a range of C$1.2452 to C$1.2512, after hitting on Thursday its strongest in more than two years at C$1.2414.

It has jumped more than 10 percent since early May, including a 3.9 percent gain last month when the Bank of Canada raised interest rates for the first time in nearly seven years.

The Bank of Canada has signaled it is comfortable with market expectations that another rate hike won't happen until October, analysts said.

Canadian government bond prices were mixed across a steeper yield curve, with the two-year up 1.5 Canadian cents to yield 1.308 percent and the 10-year falling 1 Canadian cent to yield 2.057 percent.

The 10-year yield touched on Monday its highest intraday level since November 2014 at 2071 percent.

Both Canadian and US jobs data for July and domestic trade data for June are due on Friday.