The United States is planning to re-impose tariffs on aluminum imports from Canada, Bloomberg reported late on Monday, citing people familiar with the matter.

If Canada declines to impose export restrictions, the United States will announce on Friday the re-imposition of 10 per cent tariffs on aluminum from the country, the report said.

The tariffs would then be implemented by July 1, the report said, which is also when a new Canada-U.S.-Mexico Agreement on trade is expected to take effect.

Some industries, including automakers, had been asking for a delayed implementation of the agreement due to the difficulties they are facing amid the coronavirus pandemic.

The new North American Free Trade Agreement replaces the 26-year-old trade agreement between the three economies.

The office of the United States Trade Representative did not immediately respond to a Reuters request for comment on aluminum tariffs that was sent outside regular business hours.

Earlier in the day, the U.S. Supreme Court turned away a challenge to President Donald Trump's tariffs on imported steel brought by an industry group that had argued that a key part of the law under which he imposed the duties violates the U.S. Constitution.

Trump signed a proclamation this year increasing tariffs on derivative steel products by an additional 25 per cent and on derivative aluminum products by an additional 10 per cent, from which countries including Canada and Mexico were exempted.