The prime minister discussed the unfolding situation with US Vice President Mike Pence on Thursday night.
"We have an ANZUS agreement and if there is an attack on Australia or the United States then each of us will come to the other's aid," Mr Turnbull told 3AW radio on Friday.
"In terms of defence we are joined at the hip."
Asked about Tony Abbott's call for Australia to urgently consider a missile defence system, Mr Turnbull said the country is constantly reviewing its position.
He said the advice from Defence is there is a no benefit to deploying a US-style 'Terminal High Altitude Area Defence' (THAAD) system.
"The reason for that is that THAAD's designed to provide protection for relatively small areas against short-to-intermediate range missiles," he said.
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The Vice President again told the prime minister that the US sees the way to resolve the situation as being through economic sanctions, despite Donald Trump threats of "fire and fury".
"That is the preferred way to deal with it but of course if North Korea decides to carry out some of its violent threats then obviously terrible consequences will follow," Mr Turnbull said.
Labor leader Bill Shorten believes nations need to concentrate on encouraging Pyongyang to de-escalate tensions.
"The big concern is actually not the United States, it's the bellicose and provocative actions of the North Korean dictatorship," he told reporters in Canberra.
Mr Shorten insists the government and opposition share the same concerns about North Korean leader Kim Jong-un's pursuit of nuclear missiles.
"Australians should be reassured that on this matter of North Korea and our national security, the politics of Labor and Liberal are working absolutely together," he said.
Greens leader Richard Di Natale has called on the prime minister to ditch the US alliance, and to urge an "unhinged and paranoid" Donald Trump to de-escalate the situation with North Korea.
"Malcolm Turnbull, by backing in Donald Trump, has just put a target on our back," Senator Di Natale told reporters in Canberra on Friday.
