Malcolm Turnbull says Australia would enact the ANZUS Treaty and "come to the aid of the United States" if North Korea launched an attack against the western superpower.

The Prime Minister's declaration of support follows escalating threats between America and North Korea, who earlier this week threatened to launch a multi-missile strike in the waters off the US Pacific territory of Guam.

"The United States has no stronger ally than Australia. 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," Turnbull told 3AW radio.

"If there is an attack on the United States by North Korea then the ANZUS treaty will be invoked and Australia will come to the aid of the United States, just as if there was an attack on Australia, the United States would come to our aid.

"You remember on 9/11 when the United States was attacked, John Howard invoked the ANZUS Treaty, Australia came to the aid of the United States. We stand together as we have done for generations."

Turnbull, who spoke with US Vice President Mike Pence overnight, acknowledged the conflict was "certainly the most dangerous flashpoint in the world today" but maintained the peaceful way of bringing North Korea "to its senses" was by increasing sanctions. He said China had particular influence.

While former prime ministers Tony Abbott and Kevin Rudd have urged Australia to consider a missile defence shield to protect against an attack, Turnbull said the current advice from Defence was that such a system would not be beneficial.
"What we are doing is constantly reviewing our position," he said.

"The THAAD (Terminal High Altitude Area Defence) is designed to provide protection for relatively small areas against short to intermediate range missiles ... it's not designed to provide protection against long range intercontinental ballistic missiles of the sort North Korea has recently tested," he said.

"The idea that any American president, whether it's Donald Trump or someone else, can tolerate a regime which has the capacity, assuming it has developed the capacity, it has not yet, but if it were to develop the capacity to deliver a nuclear warhead to attack an American city, the idea that that would be tolerable is absurd."

Turnbull said Trump had been speaking in language that North Korean leader Kim Jong-un "understood", after the US President warned of an event "the likes of which no one has seen" if the regime launched missiles at Guam.

"Clearly diplomatic language has not been successful and I spoke to Vice President Pence about this last night," Turnbull said.

"His view and the view of his administration is that the way to resolve the situation with North Korea, as Donald Trump reaffirmed this morning in fact, is through these economic sanctions, 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, there's no point ducking that inevitable consequence."

Turnbull said the American alliance was the "absolute bedrock of our national security" and our nations were "joined at the hip".