US President Donald Trump has formally announced he will place a 25 percent tariff on steel and aluminum imports into the United States.

The president signed documents on Monday to impose the tariff on the two key metals.

Trump said the 25 percent tariff will be applied to all trading partners and that there will be no exceptions.

The tariff rate for aluminum imports will be raised from the current 10 percent to 25 percent.

During Trump's first term, steel imports from Mexico, Canada and Australia were exempted from additional tariffs. Duty-free quotas were later granted to some countries, including Japan.

But these exceptional measures will be eliminated.

Trump said: "Our nation requires steel and aluminum to be made in America, not in foreign lands, we need to create in order to protect our country's future resurgence of US manufacturing and production."

He also said, "a lot of businesses are going to be opening in the United States."

Trump suggested that his administration is going to consider introducing tariffs on automobiles in addition to chips and pharmaceuticals among other imports.