President Donald Trump has yet to follow through on his threat to impose an additional 10 percent tariff on Canadian imports, four weeks after he halted “all trade negotiations” over an anti-tariff ad the province of Ontario ran. Trump’s announcement had Canadian exporters preparing for a worst-case scenario: a sweeping levy layered on top of existing double-digit duties. …The White House did not say whether it still plans to impose the tariff when asked for comment. But a separate US official suggested the Trump administration had opted to hold off on additional duties — which would have sent tariffs on Canadian goods to 45% — and instead continue to dangle the threat as the two sides gear up for future talks. “The Canadians know what’s on the table,” said the official. Volpe said a personal intervention by Carney in Asia last month may have helped matters, too.