At rallies and whistle-stop campaign tours, President Donald Trump proclaims a renaissance in US factories rebuilding the nation with “American steel,” “American heart” and “American hands.”

But in reality, despite his relentless use of punitive tariffs to help skew the playing field in favour of United States companies, the very industries he has tried to help have become the weakest links in the otherwise solid economy.

With just over a year to go before he faces re-election, Trump takes credit for the most vigorous economy in the industrialized world, with the expansion entering its 11th year and historically low unemployment.

But while services and office jobs dominate the US economy, Trump continues to promote the factory and mining jobs that were the lifeblood of the economy in the last century.

“American steel mills are roaring back to life,” he declared last month in Florida, the same day US Steel announced it would idle plants in Michigan and Indiana until “market conditions improve.”

And to West Virginians he said, “The coal industry is back.”

But in fact each of the sectors Trump has championed coal mining, steel, aluminium and auto manufacturing have been buffeted by a combination of market forces and changing technologies — factors beyond his control or damaged by the very things he did to protect them, economists and analysts say.

In June a national survey of manufacturing activity hit its lowest level in nearly three years narrowly avoiding slipping into contraction while regional surveys have also seen record declines.

In March, the number of workers in US manufacturing shrank for the first time in nearly two years and it is now growing more slowly than the rest of the American workforce.

“There’s clearly a rather large element of hyperbole in what the president has said,” said Scott Paul, president of the Alliance for American Manufacturing, which supported the tariffs Trump has put on steel, aluminium and Chinese imports.