In a statement delivered shortly after Mr Trump's victory speech, Mr Turnbull emphasised the "enduring national interests" of the US-Australia relationship.

"I have great confidence that all of our engagement will continue to be strong and intimate," Mr Turnbull said, singling out the challenges of tacking global terrorism and maintaining stable economic order.

"This is a historic moment. It has been a long campaign – one that Australians have witnessed with awe, with consternation, indeed, from time to time.

"But let me reassure all Australians that the ties that bind Australia and the United States are profound, they are strong, they are based on our enduring national interests."

He added: "The American people have made a great and momentous choice today."

As Mr Trump edged towards the 270 electoral collage votes needed to become America's 45th president, markets fell sharply, with the ASX dropping 2.1 per cent by the end of the day, wiping $34 billion off the value of stocks.

On Wall Street, the Dow suffered a bigger one-day fall than experienced in response to Brexit, the collapse of Lehmann Brothers, which sparked the global financial crisis, and the September 11 attacks.

Globally, stocks fell off a cliff, with $US2.5 trillion wiped off values as investors ran for the exits at the sheer unpredictability of a Trump administration.

During the longest and most bitterly fought campaign in US political history, Mr Trump had expressed contempt for America's security role in the world, floated the idea of giving nuclear arms to South Korea and Japan, vowed to keep North Korea and China in check, and proposed to tear up various trade agreements.

Prime Minister Malcolm Turnbull and Opposition Leader Bill Shorten met in the Mr Turnbull's office late on Wednesday, ostensibly to discuss constitutional recognition of Australia's first peoples. However, it is understood the US election was also up for discussion.

One Nation leader Pauline Hanson was among the few elected figures in Canberra's political establishment to enthuse about the Republican's rise.

Clutching a glass of Champagne on the forecourt of Parliament House, Ms Hanson said: "Why I am celebrating is that I can see that people are now around the world saying we've had enough of the establishment, we're sick and tired of the elites, give power back to the people to have their own democracy. And I think Donald Trump will bring that to America.

"I can see in Donald Trump a lot of me, what I stand for in Australia, and I think it's great."

Foreign Affairs Minister Julie Bishop struck a more cautious note, revealing Canberra remained in the dark on Mr Trump's foreign policy stances in trade and security, and could not predict what these policies would look like.

Choosing her words carefully, she signalled that Australia was banking on Mr Trump tempering aggressive policy stances if elected, in the hope that his professed isolationism and protectionism had been exaggerated for political campaign purposes.

"We can judge from some of the statements and the speeches made during this very long presidential campaign, but it will be a responsibility of the Australian government and other governments in the region to impress upon the new administration the importance of US leadership in our region, the importance of the United States continuing to maintain a strong presence in the region," she said.

"The new administration will have a number of challenges, including in our region, and we want to work constructively with the new administration to ensure the continued presence and leadership of the United States in our region."

Ms Bishop denied that the government had been caught out by American voters, while issuing a none-too-subtle call for like-minded countries to join Australia in pressuring Washington to stay engaged with the world in economic and strategic spheres.

"We have been preparing for either a Clinton administration or a Trump administration," she said. "We have been reaching out to both the Clinton teams and the Trump teams, and we are prepared and ready to work constructively with either administration.

"It will be incumbent upon all countries that have deep interests with the United States to ensure that they press upon the administration their concerns, their interests, but that's my expectation over the transition period."

Ms Bishop's opposition counterpart, Penny Wong, said the count in the US had thrown up a result that was not predicted in the plethora of opinion polls.

"This is not the result that many people expected, but ultimately, this is a decision for the American people," she said. "Certainly the public polling suggested something else ... what it does remind us though is that here in Australia, why it is important that we continue to respond to people's concerns around inequality."

America's most senior diplomat in Australia at present, charge d'affaires James Carouso, predicted that the US-Australian relationship would thrive either way because it was based on "much more than who is in the house, the White House or the Lodge".

"It is based on such a long history of military intelligence, economic, personal relations – this relationship is so deep, the alliance is so critical, because no matter who is going to be president, we are an Asian-Pacific nation," he said.

"The fiery rhetoric in this campaign, from both sides, has clearly heightened the concerns in the region, but I think we have to sit and wait and see what the policies of the next president are going to be. I am confident that the critical nature of the Asia-Pacific region, whoever is president, they are going to have to engage with Australia to work with our best mate in the region and how we are going to deal with whatever the issues are."

With Michael Koziol

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