Canada and the United States are finalizing a deal to close their shared border to non-essential travel — an extraordinary measure designed to slow the spread of COVID-19.

Multiple sources with direct knowledge of the talks say the details are still being worked out, and could be announced as early as Wednesday.

Once finalized, the mutual agreement would close the border to tourists and shoppers while still allowing Canadians to return home. The final deal is expected to allow some commercial traffic to continue to keep critical supply chains intact.

CNN first reported the development Tuesday night. Sources have confirmed the accuracy of the report. One source says Ottawa and Washington are working together on the plan, and that it will be reciprocal.

Prime Minister Justin Trudeau had previously resisted closing the border to Canada's closest ally and most important trading partner — but he did not rule it out.

'Sign of friendship'

The planned restrictions underscore the sudden severity of the COVID-19 crisis. Typically, Canadian officials are loath to impose restrictions on the movement of people at the border.

But the intention is to find an agreement that will restrict the free-flow of people across the border, but still allow for the flow of critical goods across the border.

On Monday, when Trudeau announced his government would deny entry to almost all foreigners, he made an exception for Americans, but said that exception would be reviewed.

A source told Radio-Canada this special treatment would have been perceived by the White House "as a sign of friendship" from Canada that would allow for goodwill in the border negotiations.

"It's a matter of time," the source told Radio-Canada, adding that there was a strong desire in Ottawa and Washington to move quickly as the COVID-19 pandemic spreads.

The agreement would limit cross-border travel to essential activities, for example, the critical delivery of goods by truck drivers.

A senior Canadian official told CBC News one of the challenges in the discussions is agreeing on what qualifies as essential travel. For example, it's unclear how strictly the rules would apply to people — on either side of the border — wanting to visit family across the border.

At a news conference earlier Tuesday in Ottawa, Deputy Prime Minister Chrystia Freeland made it clear that the government is preoccupied with finding a mutually agreeable solution to the border conundrum.

Deputy Prime Minister Chrystia Freeland said the government is preoccupied with finding a mutually agreeable solution to the border conundrum. (Justin Tang/The Canadian Press)

"Nearly 200,000 people cross that border every day and that border and that traffic that goes across that border is literally a lifeline for both the Canadians and the Americans on both sides of that border," Freeland said.

"We get our groceries thanks to truckers who drive back and forth across that border. Very urgently needed medical supplies and medicines go back and forth across that border. And essential workers go back and forth across that border every day.

"So it is a unique relationship for Canada and it's important for us in handling our situation on the border to be sure that we act to get things right."

Health Minister Patty Hajdu, whose Thunder Bay-Superior North riding in Ontario is near the Minnesota border, cited a number of examples of what the government would consider non-essential travel, such as shopping trips by residents of border communities — "things that people have taken for granted in a border town for a very long time."

President Donald Trump, asked about the prospect of closing the northern border at his own White House news conference earlier in the day, signalled that talks were in progress.

'Trusted trader'

"I don't want to say that, but we are discussing things with Canada, and we are discussing things with Mexico, quite honestly. The relationship is outstanding with both — outstanding," Trump said, citing in particular the Canada-U.S.-Mexico Agreement, which Canada finally approved late last week before temporarily shutting down Parliament.

"We're working very closely with Canada. Canada has closed (its border) to the world, but they have not closed it to the United States."

Dan Ujczo, a trade lawyer in Columbus, Ohio, who specializes in Canada-U.S. issues, said business and trade interests in the two countries, along with governments at every level, have been working on solutions ever since the terrorist attacks of Sept. 11, 2001 exposed the absence of suitable contingency plans.

Since then, so-called "trusted trader" programs like Free and Secure Trade and Partners in Protection have advanced the idea that whatever the circumstances, cross-border commerce must be allowed to continue, he said.

"Companies enrolled in these programs likely will have continued access to ensure cross-border trade."