Malcom Turnbull steps into the G20 today amid talk of war over North Korea's determination to arm itself with intercontinental ballistic missiles.

"Everybody's goal is to ensure that the North Korean regime as I've said is brought to its senses, that it stops this reckless escalation so that the peace of the region is no longer threatened by its conduct," he told journalists in Hamburg.

He will have to tread very carefully in what has become yet another venue in a dangerous dance for strategic advantage between the world's major powers.

He has been a loud voice in a US-led chorus accusing China of not doing enough to haul in the mad client state on its border.

"The actions by the North Korean regime are illegal, they are dangerous, they're a provocation and they've been escalating them," Mr Turnbull said.

"The nation with the greatest leverage over North Korea is China."

The rhetoric was turned up when the US ambassador to the United Nations pointed to America's "considerable military forces" which it would use "if we must" to end the threat posed by North Korea's nuclear ambitions.

But on the way to the G20, China's President Xi Jinping went to Moscow to form a united front with Russia's Vladimir Putin.

They called on North Korea to suspend its ballistic missile program and for the US and South Korea to back off on the deployment of an anti-missile system that China also sees as a threat.

This deft step makes North Korea and the US seem equally culpable for the threat to peace on the Korean peninsula.

Turnbull talks up sanctions, Trump warns of 'severe things'

By comparison, on Thursday Donald Trump warned North Korea he was considering "some pretty severe things" if it did not abandon its missile development in the coming weeks and months.

He would not say what those things might be.

Sorry, this video has expired Donald Trump said "something will have to be done" about North Korea. (Photo: AP/Czarek Sokolowski)

Mr Turnbull would not speculate on potential military action and refused to speculate about imposing trade sanctions against China as a way of pressuring it to do more to influence North Korea.

Instead he emphasised the trade measures taken against North Korea itself.

Sorry, this video has expired Mr Turnbull received a warm welcome from a passerby in Hamburg

"We are a party to and of course support the sanctions imposed by the United Nations and we also have autonomous sanctions of our own against North Korean entities and individuals," Mr Turnbull said.

"But we will work cooperatively through the United Nations and taking measured steps autonomously, but focused on bringing the economic pressure to bear on North Korea to bring that regime to its senses without conflict."

But after all the bluster, more sanctions on North Korea would look weak. The only ones that would look strong involve targeting China, and that risks a trade war with country armed with considerable economic weapons of its own.

So, as it stands, China and Russia have the whip hand. They have a plan with the dual benefits of sounding sensible and allowing plenty of room to manoeuvre if North Korea continues to develop nuclear capable missiles as everyone assumes it will.

The next steps for the US are all bad: military action, third country trade sanctions, or a retreat to the failed prescriptions of the past.

Mr Trump says he does not "draw red lines" like his predecessor. But given his lack of options on North Korea his stance is redolent of Barack Obama's strategic miscalculation in Syria.

Then Mr Obama declared the Assad regime would cross a "red line" if it used chemical weapons in the civil war. The weapons were used, America did nothing and its bluster was exposed.

Ever since Russia has appeared to have a clearer idea of its mission in Syria than the US and its allies.

That was articulated at the last G20 in a meeting between Mr Putin and Mr Turnbull.

"I'm fighting for the legitimate Government of Syria," Mr Putin told Mr Turnbull. "Who are you fighting for?"

It was, Australian sources conceded at the time, a very good question.

On the face of it, it looks as if the US has, again, worked itself, and Australia, into an unplayable diplomatic position.

So far, Mr Turnbull has echoed the US line that China needs to "do more" to haul in the hermit kingdom. If it does not, where do Australia and the US go?