SYDNEY - US President Donald Trump’s decision not to exempt Australia from his latest tariffs has sparked immediate concerns about the future of the relationship between the stalwart allies, including whether Washington will stick to a deal to provide nuclear-powered submarines.

Australian Prime Minister Anthony Albanese on March 13 condemned the “disappointing” tariffs decision and urged Australians to buy locally made products rather than US products, but he rejected calls to retaliate by imposing tariffs on the US.

He said he would not cancel plans to buy American nuclear-powered submarines as part of the three-way Aukus pact between Australia, the United States and the United Kingdom.

“The Aukus deal stands by itself as a good deal for Australia,” he told ABC Radio. “We’re not doing it as a favour (to Washington). We’re doing it as a way of best defending our island continent.”

The US president’s decision to impose 25 per cent tariffs on steel and aluminium is expected to have only a limited effect on the Australian economy. Australia exports about A$1 billion (S$840 million) worth of steel and aluminium to the US each year.

But the move has raised questions about whether the US can be trusted to deliver the submarines and about the impact on the long-term security relationship between the two countries.

A former head of the Australian Defence Force, Admiral (ret) Chris Barrie, told The Sydney Morning Herald on March 13 that the tariff decision showed that “no agreement (with the Trump administration) is secure”. He said Australia needed to develop alternative submarine plans in case the Aukus acquisitions did not proceed.

“It is important for us to develop a plan B because of the real possibility the US will never give us the submarines because they need them for themselves,” he said.

An international relations expert, Professor Mark Beeson, an adjunct professor at the Australia-China Relations Institute at the University of Technology Sydney, told The Straits Times that the government had pinned its future security on an A$368 billion plan to acqu...