The Canada-U.S. border will likely be closed to non-essential travel by Friday night as the two countries move quickly to curtail the rapid spread of the new coronavirus, Prime Minister Justin Trudeau said Thursday.

“We are working on the final details with the U.S. but we expect the measures to come into effect sometime during the night between Friday and Saturday… in about a day and a half,” Trudeau told reporters from Rideau Cottage in Ottawa, where he is under self-isolation after his wife tested positive for the virus last week.

The ban on non-essential travel across the border was first announced Wednesday. Trudeau, who finalized the agreement in a phone call with U.S. President Donald Trump, said the decision came out of a need to follow public health advice.

There are exceptions to the ban, including aircrews, diplomats, and healthcare workers.

Trudeau made clear that “essential travel” won’t stop and that the new measures will not disrupt the flow of supply chains bringing essential goods like food, fuel, medicines and other services into either country.

That sentiment was echoed by Deputy Prime Minister Chrystia Freeland, who said keeping the supply chain moving was vital to the $2.7 billion worth of goods that flow through the Canada-U.S. border daily.

She reiterated that on Thursday, adding that the government is working very hard to finalize details of the closure by Friday night.

It’s not yet known how long the border closure will be in place.

Trump previously suggested it could be about a month, but a hard timeline isn’t likely, as the global health emergency remains fluid.