Washington — President Trump’s nominee to be ambassador to Canada affirmed the nation’s sovereignty on Thursday amid the president’s repeated threats to make it part of the United States. 

“Canada is a sovereign state, yes,” Pete Hoekstra said during his confirmation hearing when asked by Democratic Sen. Chris Coons of Delaware whether he agreed that Canada is an independent nation and that it “should not be even jokingly referred to as the 51st state.” 

Hoekstra also said that the two countries “have a great history of working together.” He added that Mr. Trump’s priorities of “freer, fairer trade” would “grow the business relationship” with Canada. 

On Thursday, Mr. Trump questioned the international boundary between the U.S. and Canada, calling it an “artificial line” that somebody drew decades ago. 

“Makes no sense,” he said. 

This week, Mr. Trump imposed 25% tariffs on steel and aluminum imports from Canada and threatened to double the levies if the country did not suspend its new 25% surcharge on exports of electricity to several U.S. states. 

Mr. Trump has justified the tariffs as protecting U.S. interests, though the existing trade agreement with Canada was negotiated and signed by him during his first term. The president suggested that Canada should acquiesce to his requests for annexation to alleviate the economic pressure. 

“The only thing that makes sense is for Canada to become our cherished Fifty First State,” Mr. Trump wrote Tuesday. “This would make all Tariffs, and everything else, totally disappear. Canadians’ taxes will be very substantially reduced, they will be more secure, militarily and otherwise, than ever before, there would no longer be a Northern Border problem, and the greatest and most powerful nation in the World will be bigger, better and stronger than ever — And Canada will be a big part of that.”