The United States is set to impose 25 percent of tariff on steel imports products and 10 percent on aluminum, Trump said after a meeting with business executives at the White House.

"We'll be signing it next week. And you'll have protection for a long time in a while," said Trump.

News of the tariffs immediately hit sentiment on the Wall Street, with the Dow slumping over 500 points, more than 2 percent, in late trading.

In response, Canadian Trade Minister Francois-Philippe Champagne said that any U.S. tariff or quota imposed on Canada's steel industry would be "unacceptable."

Daniel Ikenson, a senior fellow at the Cato Institute, said on Thursday that trade restrictions could hurt U.S. producers by exposing them to competitions from foreign rivals with lower production costs capable of offering lower prices in the U.S. market.

U.S. actions would face legal challenge by other World Trade Organization members, and they would also invite other members to invoke national security to protect favored industries, said Ikenson.

European Union (EU)'s trade chief Cecilia Malmstrom has said that the EU would seek retaliation measures if the Trump administration's 232 trade investigation brings damage to European steelmakers.

It's still unknown whether Trump's announcement on Thursday refers to blanket tariffs for all countries.

In April last year, Trump ordered the Commerce Department to study the impact of steel and aluminum imports on national security under seldom-used section 232 of the 1962 Trade Expansion Act.

Two weeks ago, the Commerce Department unveiled its recommendations for Trump to restrict imports of steel and aluminium products due to national security concerns, which drew oppositions from U.S. lawmakers and businesses.

According to recommendations by the Commerce Department, the United States could introduce at least 24 percent tariff on all steel imports from all countries and at least 7.7 percent tariff on all aluminium imports from all countries.

Trump's announcement was higher than both recommendations.

Wendy Cutler, former Acting Deputy U.S. Trade Representative and now vice president at the Asia Society Policy Institute, said "the imposition of tariffs on steel and aluminum will also reverberate throughout the U.S. economy and possibly negate some of the benefits of the recent tax cuts."