White House economic adviser Kevin Hassett said on Sunday he was hopeful a dispute with Canada over accusations of the deadly fentanyl opioid entering the U.S. across its northern border could be resolved by the end of March.

Trump at first imposed 25% tariffs on Canadian and Mexican exports to the U.S., then exempted the duties on Mexican- and Canadian-made vehicles being transported into the U.S. and later by week’s end delayed the tariffs on almost all items for four weeks until April 2.

White House adviser Kevin Hassett suggests a dispute with Canada over fentanyl smuggling into the U.S. might be resolved by March's end. The contention has led to potential tariffs from President Trump,