Justin Trudeau, the Canadian Prime Minister, told President Donald Trump on Wednesday he would block his country’s armed forces from buying Boeing aircraft if the US presses ahead with plans to slap import tariffs of 300 percent on Bombardier aeroplanes.

The issue is threatening to ignite a trade war between the US, Canada and the UK, where the Canadian planemaker employs about 4,000 people in Belfast.

Mr Trudeau met the US President at the White House for talks on the North American Free Trade Agreement and said he raised the issue of Bombardier “directly”, outlining his opposition to US anti-dumping policy.

“I highlighted to the president how we disagree vehemently with Commerce’s decision to bring in countervailing and anti-dumping duties against Bombardier, that we feel this is not something that is warranted and quite frankly something that we look very negatively upon,” he said after the meeting.

“The attempts by Boeing to put tens of thousands of aerospace workers out of work across Canada is not something we look on positively.”