Canada and the United States have agreed to keep their shared border  closed until at least July 21, Prime Minister Justin Trudeau announced Tuesday.

The world's longest international border, at 8,900 kilometers (5,500 miles), was shut to all non-essential travel on March 21 in response to the coronavirus crisis, and the closure has been extended twice already.

"I can now confirm that Canada and the United States have once again, agreed to extend by 30 days until July 21 the current measures in place along our border," Trudeau told a daily briefing.

"This is an important decision that will keep people in both of our countries safe," he said.

Prior to the pandemic, Can$2.4 billion (US$1.7 billion) worth of goods and more than 400,000 people crossed the border each day on average.

Its closure has led to a massive drop in cross-border traffic -- of up to 95 percent, according to Statistics Canada -- but trade has continued unabated.