US alliance safe despite election uncertainty: minister

Multi-billion dollar plans for Australia to buy nuclear submarines from America will be safe regardless of who wins the US election, the defence minister says.

As campaigning enters its final day, polls show Donald Trump and Kamala Harris neck and neck in the race for the White House.

Defence Minister Richard Marles says the US/Australia alliance will remain secure, no matter which party wins the presidency.

"Australia's alliance with the United States will remain strong and the major equities that we have in that alliance - for example AUKUS and acquiring our future submarines - that will remain on track," he told Seven's Sunrise program on Tuesday.

"We have worked very closely with people across the political spectrum of the United States: Democrats, Republicans, Trump Republicans and all of them are supportive of the Australian alliance, supportive of AUKUS and what we are doing."

Polls will close on Wednesday, Australian time, with the path to victory to come down to a handful of swing states such as Pennsylvania, Wisconsin and Georgia.

Ms Harris is vying to be the first woman president, while if Mr Trump wins, he would be the first person in more than 130 years to serve non-consecutive terms in the White House.

After rioters stormed the US Capitol trying to overturn the election results after the 2020 election following Mr Trump's loss, opposition foreign spokesman Simon Birmingham said he hoped there would not be unrest following the 2024 poll.

"We hope to see an election outcome that is respected by all sides, and that does see a peaceful transition of power from President Biden to either a new president. Harris or a returned President Trump," he told Sky News.

"Clearly, there are very strong and passionately held views on both sides. But the US has seen enormous tests and strain before."

Opposition senator Dave Sharma said Australia would work well with either side of US politics following the election.

"(A Harris presidency) will largely be a continuation of the Biden administration, with whom we've got good relations," he told ABC TV.

"By the same token, I think if we're dealing with the Trump administration, I don't actually think it necessarily means a whole lot for Australia."

However, Mr Trump's views were out of touch with the mainstream and could pose a risk to Australia's national interests, international policy expert Michael Fullilove said.

If he regains the presidency, it would be "extremely discombobulating for us allies around the word", the Lowy Institute director said.

"Mr Trump is profoundly sceptical of alliances, he has a weird affinity for strongmen," he told AAP.

"It's all personal and it's all transactional so that affects the reliability the rest of the world associates with the US."

It would leave allies and leaders questioning how best to interact with a Trump administration, Dr Fullilove said.

"Should we be critical? Should we be sycophantic? How do we manage this very difficult, complicated relationship?" he said.

A president hostile to free trade could also send shocks through the international system, Dr Fullilove said, with Mr Trump threatening tariffs against China.

That would hurt Australia as China's massive economic influence meant "if they get the flu we're going to get a cold", he said.

While Ms Harris has more mainstream views, she did remain somewhat of an unknown quantity regarding foreign policy as she wasn't a major player in the field during her vice presidency, he said.

"But based on speeches we expect her to be a conventional US president," he said.