U.S. Ambassador to Canada Pete Hoekstra addresses the Global Business Forum in Banff, Alta., in September.

The American ambassador to Canada delivered an expletive-filled dressing-down to Ontario’s representative in Washington during a prestigious event in Ottawa on Monday, according to two sources, who said the tirade focused on an anti-tariff ad commissioned by the province .

U.S. Ambassador Pete Hoekstra confronted David Paterson, a former General Motors auto executive now working as Ontario’s representative, at the annual Canadian American Business Council gala at the National Art Gallery.

The sources told The Globe and Mail that Mr. Hoekstra began to swear at Mr. Paterson over the Ontario ad, which has riled up U.S. President Donald Trump . The President cited the ad as the r

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