Australia's ambassador to Washington, Joe Hockey, has predicted the North Korea standoff "has to come to a head" – including possibly through military action – and firmly backed President Donald Trump's "unconventional" approach to the nuclear crisis.

Mr Hockey also said during a visit to Canberra on Friday that Australian cities were targets for the hermit regime of Kim Jong-un and needed to be protected.

"Rolling over and tickling the tummy of Kim Jong-un is not the answer. It's just not," he said. "We're a target. Our cities are targets. Our people are targets. This guy's unhinged and we've got to protect our people as the United States has to protect its people."

Mr Hockey effectively defended what some commentators have branded Mr Trump's "mad man theory" approach - acting unconventionally to break the previous patterns of predictability that had failed to curb the regime's nuclear program.