U.S. President Donald Trump on Tuesday signed a proclamation raising his tariffs on steel and aluminum to 50% from 25%, making good on his earlier threat of higher levies on the two commodities.

Trump said that the move was aimed at bolstering U.S. national security, which he claimed was compromised by the country's heavy dependence on steel and aluminum imports. The higher duties will be effective from Wednesday.

"I have determined that it is necessary to increase the previously described steel and aluminum tariffs to adjust the imports of steel and aluminum articles and their derivative articles so that such imports will not threaten to impair the national security," Trump wrote in the proclamation, which was posted to the White House website.

Trump said the tariffs will dissuade dumping in the U.S. by other countries, and also boost the competitiveness of American steel producers. Steel and aluminum derivative products will also be subject to the duties.

The UK, however, will be exempt from the increased tariffs, Trump said, in accordance with a trade deal signed in early-May. Tariffs on UK steel and aluminum imports will remain at 25%.

Higher import tariffs on the materials herald increased costs for U.S. businesses, given that they will be borne by U.S. importers. Trump's tariffs are aimed at dissuading imports and pushing local businesses into sourcing materials from domestic producers.

But his tariffs are expected to further ramp up costs for steel and aluminum consumers, undermining local manufacturing, which depends heavily on imports of the two.

Setting up local infrastructure for more aluminum and steel production is expected to take years, with companies facing substantially higher costs in the interim.

Source: Investing.com