The White House formally announced late Thursday that six countries and members of the European Union (EU) would be temporarily exempt from President Trump Donald John TrumpBubba Wallace to be driver of Michael Jordan, Denny Hamlin NASCAR team Graham: GOP will confirm Trump's Supreme Court nominee before the election Southwest Airlines, unions call for six-month extension of government aid MORE's tariffs on steel and aluminum imports.

Trump authorized an exemption for Argentina, Australia, Brazil, Canada, Mexico, South Korea and all 28 EU member countries while the U.S. negotiates long-term plans with foreign leaders from each country and the European body.

Trump will decide by May 1 whether to extend each exemption depending on the status of those talks, the White House said.

U.S. Trade Representative Robert Lighthizer Robert (Bob) Emmet LighthizerWhiskey, workers and friends caught in the trade dispute crossfire GOP senator warns quick vote on new NAFTA would be 'huge mistake' Pelosi casts doubt on USMCA deal in 2019 MORE had said earlier Thursday during a hearing on Capitol Hill that Trump had decided to pause the tariffs for those countries.

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The exemption applies to the top four exporters of steel to the United States — Canada, Brazil, South Korea and Mexico — which collectively account for about 50 percent of the steel imported into the United States.

Trump announced on March that the U.S. would impose tariffs of 25 percent on steel imports and 10 percent on aluminum imports for national security reasons, in a move he argued would protect domestic workers and benefit U.S. companies.

The tariffs are set to go into effect on Friday for all other nations that send their metals to the United States, including countries such as Japan, China, Russia, India and Turkey.

Lawmakers from the president's own party and leaders from around the world warned Trump against imposing the tariffs, saying they could spark a trade war.

Trump has brushed off those concerns, but China on Thursday announced it is prepared it implement reciprocal tariffs after the U.S. moved to specifically impose additional levies on Chinese products amounting to $50 billion.