The US Secretary of State Rex Tillerson has called on the world to step up pressure on North Korea to end its nuclear programme.

He's joined a summit in Canada discussing how to tighten sanctions on Pyongyang.

Russia and China were excluded from the meeting, only countries that had supported Seoul during the Korean War were invited to the summit.

Moscow and Beijing said this one-sided gathering could aggravate tensions.

Twenty nations have agreed to consider tougher sanctions to press North Korea to give up its nuclear weapons and Tillerson warned Pyongyang it could trigger a military response if it did not choose negotiations.

A US-hosted meeting of countries that backed South Korea during the 1950-53 Korea War also vowed to support renewed dialogue between the two Koreas “in hopes that it leads to sustained easing of tensions” and agreed that a diplomatic solution to the crisis was both essential and possible on Tuesday.

North Korean maintains that it has the right to advance its missile technology and does not agree to stop developing its nuclear missiles capability, which it says is a deterrent against possible foreign aggression.

UN has placed sanctions on North Korea in order to force Pyongyang to give up its missile and nuclear technologies.

The United States and Canada co-hosted the day-long meeting in Vancouver to discuss ways to increase pressure on Kim.

US officials have reported a debate within the Trump administration over whether to give more active consideration to military options, such as a pre-emptive strike on a North Korean nuclear or missile site.

Tillerson brushed off a question about such a “bloody nose” strike, telling a closing news conference: “I’m a not going to comment on issues that have yet to be decided among the National Security Council or the president.”

However, he said the threat posed by North Korea was growing.

“We all need to be very sober and clear-eyed about the current situation ... We have to recognise that the threat is growing and if North Korea does not choose the pathway of engagement, discussion, negotiation, then they themselves will trigger an option,” Tillerson said.

“Our approach is, in terms of having North Korea chose the correct step, is to present them with what is the best option – talks are the best option; that when they look at the military situation, that’s not a good outcome for them.”

“It is time to talk, but they have to take the step to say they want to talk.”

The Vancouver meeting pledged to ensure that UN sanctions already in place were fully implemented and the participants said in a joint statement they agreed “to consider and take steps to impose unilateral sanctions and further diplomatic actions that go beyond those required by UN Security Council resolutions.” They gave no details.

Tillerson said all countries needed to work together to improve interdiction of ships attempting to skirt sanctions and said there must be “new consequences” for North Korea “whenever new aggression occurs.”

He said the meeting had agreed that China and Russia, which did not attend the Vancouver talks and sharply criticized them, must fully implement UN sanctions.

Speaking in Beijing, Chinese Foreign Ministry spokesman Lu Kang said Canada and the US were demonstrating a “Cold War mentality” that would divide the international community and damage chances of an appropriate settlement on the peninsula.

“Only through dialogue, equally addressing the reasonable concerns of all parties, can a way to an effective and peaceful resolution be found,” Lu added.

US officials say discussion of a military strike option has lost some momentum since North and South Korea held formal talks for the first time in two years this month and Pyongyang said it would send athletes to the Winter Olympics that South Korea will host next month.