Trudeau said U.S. citizens are exempt from the ban because Canada's southern neighbor is in a category of its own.

Canada will also strengthen travel restrictions in other areas.

Trudeau said that, starting Thursday, international flights will only be permitted to land in four cities' airports: Toronto, Montreal, Vancouver and Calgary. He said flights to Canada from the U.S., Mexico, the Caribbean and Saint Pierre and Miquelon will be exempt from this rule.

Airlines, he added, will be mandated to test all travelers and to prevent anyone showing symptoms of the virus from boarding a plane.

The prime minister said Canadians returning home from abroad will have to self-isolate for 14 days.

Earlier Monday, the Canada Border Services Agency added new questions for travelers arriving in Canada from all international destinations. The change, aimed at dealing with coronavirus fears, came amid confusion and criticism of the government’s airport screening process.

Ontario Premier Doug Ford called on the federal government earlier Monday to tighten things up at the border.

Ford also said he would support a federal government decision to shutter Canada's borders to visitors, including those from the United States, in response to the coronavirus. But Ford added that he would not want to see any closure to cross-border trade and commerce.