West Mifflin, 31 May

US President Donald Trump on Friday told Pennsylvania steelworkers he's doubling the tariff on steel imports to 50 per cent to protect their industry, a dramatic increase that could further push up prices for a metal used to make housing, autos and other goods.

In a post later on his Truth Social platform, he added that aluminium tariffs would also be doubled to 50 per cent, and both tariff hikes would go into effect Wednesday.

Trump spoke at US Steel's Mon Valley Works–Irvin plant in suburban Pittsburgh, where he also discussed a details-to-come deal under which Japan's Nippon Steel will invest in the iconic American steelmaker.

Although Trump initially vowed to block the Japanese steelmaker's bid to buy Pittsburgh-based US Steel, he reversed course and announced an agreement last week for what he described as “partial ownership” by Nippon.

“We're here today to celebrate a blockbuster agreement that will ensure this storied American company stays an American company,” Trump said as he opened an event at one of US Steel's warehouses.

Steel prices have climbed 16 per cent since Trump became President in mid-January, according to the government's Producer Price Index.