US President Donald Trump appears set to avoid slapping steel and aluminium tariffs on Australia after intense lobbying by Australian officials, who argued the tariffs would pose a national security risk.

On Friday morning, Mr Trump talked up the US-Australian relationship and indicated Australia would be an ally that would not face the tariffs.

"We have a very close relationship with Australia," Mr Trump told reporters. "We have a trade surplus with Australia. Great country. Long term partner. We will be doing something with them."

Later, at a signing ceremony at the White House, Mr Trump said Canada and Mexico was officially exempt from the tariffs while he indicated "great partners and military allies" may also sidestep America's 25 per cent tariffs on steel imported into the US and 10 per cent on aluminium.