Tillerson warns military action on N Korea

US Secretary of State Rex Tillerson has warned that if North Korea does not negotiate on giving up its nuclear weapons, it could trigger a military response.

After a meeting of US allies in Canada on how to beef up the sanctions pressure, Tillerson stressed that the Trump administration seeks a diplomatic resolution in the nuclear standoff.

But he said the North has yet to show itself to be a "credible negotiating partner."

He said US-North Korea talks would require a "sustained cessation" of threatening behaviour.

Tillerson declined to comment on whether the White House is considering limited military action against Pyongyang, in response to reports that some in the Trump administration advocate military action to give the North a "bloody nose."

"We all need to be very sober and clear-eyed about the current situation," Tillerson said when he was asked whether Americans should be concerned about the possibility of a war.

He said North Korea has continued to make significant advances in its nuclear weapons through the thermonuclear test and progress in its intercontinental missile systems.

"We have to recognise that the threat is growing and that if North Korea does not choose the pathway of engagement, discussion, negotiation then they themselves will trigger an option," he said.

His uncompromising message came after a gathering in Vancouver, where there was scepticism among the allies over North Korea's sincerity in its recent diplomatic opening with the US-allied South.

The meeting convened days after a mistaken missile alert caused panic on Hawaii, a stark reminder of the fears of conflict with the North.

South Korean Foreign Minister Kang Kyung-wha said its talks with North Korea, leading to the North's participation in next month's Olympics being hosted by the South, are a "significant first step toward restoring inter-Korean relations."

But she conceded that despite the overtures, North Korea has yet to show any intention to fulfill its obligations on denuclearisation of the Korean Peninsula.

China, which did not attend the meeting, said on Wednesday the gathering showed a Cold War mentality and would only undermine a settlement of the North Korea problem.