It is not yet known whether Australian steel and aluminium exports will be included.

“Any steel coming into the United States is going to have a 25 per cent tariff,” he told reporters Sunday on Air Force One as he flew from Florida to New Orleans to attend the Super Bowl.

When asked about aluminium, he responded, “aluminium, too” will be subject to the trade penalties.

Trump also reaffirmed that he would announce “reciprocal tariffs” —”probably on Tuesday or Wednesday” — meaning that the US would impose import duties on products in cases where another country has levied duties on US goods.

“If they are charging us 130 per cent and we’re charging them nothing, it’s not going to stay that way,” he told reporters.

According to the United Nations COMTRADE database, Australian iron and steel exports to the US were worth about $378 million ($US237 million).

Australian exports of aluminium are worth about $503 million.

The Australian Stock Exchange (ASX) is expected to plunge this morning in response to the news.

Trump’s comments are the latest example of his willingness to threaten and impose import taxes.

Tariffs are coming much earlier in his presidency than during his previous four years in the White House, when he prioritised tax cuts and deregulation.

Trump has alternately said he sees import taxes as tools to force concessions on issues such as immigration, but also as a source of revenue to help close the government’s budget deficit.

– Reported with Associated Press