The uncompromising comments came as a surprise, since Ottawa has enjoyed smooth relations with the US recently.

Canada on Thursday attacked a proposal by the United States to deploy troops along the undefended joint border to help fight the spread of coronavirus, saying the idea was unnecessary and would damage relations.

The uncompromising comments came as a surprise, since Ottawa has enjoyed smooth relations with the administration of US President Donald Trump over the past 18 months. Last week the two nations agreed to close the border to non-essential travel to ease the strain on health systems from the outbreak.

Canadian Deputy Prime Minister Chrystia Freeland, however, made clear the Liberal Party government had no time for a plan to send hundreds of troops to the border to help boost security.

“Canada is strongly opposed to this US proposal and we have made that opposition very, very clear … this is an entirely unnecessary step which we would view as damaging to our relationship,” Freeland told a news conference.

“The public health situation does not require such action,” she said, noting Washington had yet to take a final decision.

A US official said the proposed deployment would help border patrol officers enforce the ban on non-essential travel by providing communications and monitoring capabilities.

The Canada-US border stretches 8,891 km (5,525 miles), touches three oceans and is a crossing point for one of the world’s largest bilateral trading relationships.

“Symbolically speaking … it’s important for us to have an unmilitarised border between neighbouring countries that have been friends for a very long time,” said Freeland.

Ottawa feels the best way to prevent the deployment is to speak out strongly in public and private to ensure Washington gets the message, said a Canadian official who asked to remain anonymous, given the sensitivity of the situation.

There was no immediate reaction from the White House.

Canadian Prime Minister Justin Trudeau earlier said Ottawa was in constant touch with US authorities and would adjust border security measures if needed.

The US state of New York, which shares a border with Canada, has been an epicentre of the US outbreak.

Tim Currier, the mayor of Massena, New York, a town of about 13,000 people that is located about 15 km (9 miles) from the border, said the deployment of troops could spark panic if it were not communicated properly.

“I’m concerned about perception. I’m concerned about how citizens look at that,” he said in a telephone interview.

Canada has confirmed 3,409 coronavirus cases and 35 deaths, medical officials said.