Washington DC - President Donald Trump on Monday unveiled plans to build what he called America's biggest-ever steel plant in Iowa, a crucial battleground state for midterm elections in a few weeks.

Trump's announcement of the $15 billion facility is aimed at giving struggling Republicans a positive message amid rising voter anger over living costs and the stalled war with Iran.

"Today we're thrilled to announce that Mesabi Metallics will be building the largest steel plant in American history in the great state of Iowa," Trump said in the Oval Office.

The White House said the steel mill would cost $15 billion and use ore from Mesabi's new iron mine in Minnesota, which it said was the first new such mine in the US for 50 years.

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Iowa is one of several states that Republicans would normally expect to hold comfortably but are now regarding nervously ahead of November's midterm elections.

Trump won Iowa convincingly in the 2024 presidential election, but Republican Senate candidate Ashley Hinson – who was alongside him in the Oval Office – currently trails her Democratic rival in the polls.

Republicans risk losing control of not only the House of Representatives in the midterms but also the Senate, which would torpedo Trump's legislative program and put him at risk of a third impeachment.