U.S. refiners have become more reliant on heavy crude from Canada. Tariffs on Canadian crude oil imports could lead to higher gasoline prices for U.S. drivers.

The 10 percent tariff the president said he might impose in March could cause U.S. refineries to cut production and lead to higher prices.

The U.S. has become reliant on their crude, and Canada has ways to limit any financial hit.

Oil prices extended gains on Tuesday amid concerns over Russian and Iranian oil supply and sanctions threats despite worries that escalating trade tariffs could dampen global economic growth. Brent crude futures were up $1.