"It is critical that we preserve supply chains between both countries," Trudeau said.
"These supply chains ensure that food, fuel and life-saving medicines reach people on both sides of the border."
Trudeau made his comments in front of his residence where he is self-isolating after his wife tested positive for the virus.
Truck drivers and Canadian snowbirds, who live in the US for part of the year and are returning to Canada, are among those exempted.
Completely closing the border would cause severe damage to two economies so closely integrated.
Much of Canada's food supply comes from or via the US, and 98 per cent of its oil exports go to the US.
The United States has seen about 6500 coronavirus cases and more than 110 deaths, compared with about 600 cases and eight deaths in Canada.
No final decisions have been made about the changes under consideration for the Mexican border, according to the Trump administration officials. The administration sees Mexico's efforts to check the spread of the virus as among the weakest in the Americas.
The officials said Trump would use powers available during emergencies such as the coronavirus pandemic to undertake what would be one of the most aggressive attempts to curtail illegal immigration. If the US Surgeon General determined there was a "serious danger" of bringing a communicable disease to the United States, then Trump could rely on a law giving him authority to deny entry to people or to reject cargo, the officials said.
There were more than 851,000 arrests for crossing from Mexico into the US during the budget year that ended September 30. The policy being considered would not apply to asylum-seekers who present themselves at land ports of entry, the officials said.
They were not authorised to discuss the matter publicly because the plan has not been announced, and they spoke on condition of anonymity.
The situation at Canada's border came into focus Monday when Trudeau said that he would close the country's borders to anyone who was not a Canadian citizen, an American or a permanent resident. Even then, those people are required to self-isolate for 14 days on arrival.
Canadian Deputy Prime Minister Chrystia Freeland said the border was vital to the daily life to people on both sides.
"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."
But many in Canada criticised the decision to give Americans an exemption, including British Columbia Health Minister Adrian Dix, citing the surge in cases in neighbouring Washington state.
Robert Bothwell, a professor of Canadian history and international relations at the University of Toronto, said the government-to-government accord merely ratifies what is already in place.
"Tourism in the age of the coronavirus is a contradiction in terms," Bothwell said.
"And no Canadian in his or her right mind would want to be caught with the virus on the US side of the border, given the predatory US medical pricing system. Actually, the insurance companies have already taken care of the problem. Many of us have received notices that they will not pay for virus treatment south of the border."
For most people, the coronavirus causes only mild or moderate symptoms, such as fever and cough. For some, especially older adults and people with existing health problems, it can cause more severe illness, including pneumonia. The vast majority of people recover from the new virus. According to the World Health Organisation, people with mild illness recover in about two weeks while those with more severe illness may take three weeks to six weeks to recover.
- AP
