The United States and its allies on Tuesday vowed tougher measures to halt North Korean sanctions busting, including naval security operations to prevent maritime smuggling.
Secretary of State Rex Tillerson and Canada's foreign minister Chrystia Freeland, hosts of talks in Vancouver, urged world powers to support "maritime interdiction" measures.
And, along with Japan, South Korea and the other powers gathered for the high-level meeting, they re-committed to "the complete, verifiable and irreversible de-nuclearization of the Korean peninsula."
The warning of robust new tactics to intercept illicit shipments of nuclear materials or sanctions-busting imports was the most concrete measure to come out of a two-day meeting to which China and Russia were not invited.
Many observers, including Beijing and Moscow themselves, had questioned the value of holding a meeting of former Korea War allies to discuss an issue when China's support remains the key to diplomatic success.
Others had noted a stark difference in tone between the hawkish Japanese envoy, Foreign Minister Taro Ono, and South Korea's more cautious Kang Kyung-Wha, who said recent inter-Korea talks were a sign sanctions are already working.
But after the meeting was done, Tillerson insisted the allies will remain united and continue to work with China and Russia to enforce UN-backed sanctions and force Kim Jong-Un to negotiate his own nuclear disarmament.
"Our unity and our common cause with others in the region, most particuarly China and Russia, will remain intact despite North Korea's frequent attempts to divide us and sow dissension," he said.
"We discussed the importance of working together to counter sanctions evasion and smuggling and we also issued a call to action to strengthen global maritime interdiction operations to foil illicit ship-to-ship transfers."
North Korea has been accused of seeking to evade the draconian sanctions imposed on its isolated regime by transferring supplies from foreign vessels to its own on the high seas.
Some experts have argued that naval action to intercept merchantmen would be interpreted as an act of war and trigger a potentially devastating North Korean response.
And reports in Washington suggest that US forces are at least planning for a potential strike of their own, a limited so-called "bloody nose" strike to convince Kim that his safest option is a negotiated settlement.
Tillerson refused to address military planning issues, and would not say whether US President Donald Trump has been in contact with Pyongyang, but he did warn that the crisis is coming to a head.
"With respect to whether Americans need to be concerned about a war with North Korea, I think we all need to be very sober and clear eyed about the current situation," he warned, just days after a false warning of a missile strike jolted the US island state of Hawaii.
Tillerson said that North Korea's recent tests of a thermonuclear warhead and of an intercontinental missile show their "continued progress" in developing an arsenal that is already a global threat.
"I think our approach is in terms of having North Korea choose the correct step is to present to them that talks are the best option, that when they look at the military situation, that's not a good outcome for them," he said.
- Is North Korea 'buying time'? -
The delegates broadly welcomed North Korea's decision to meet with Seoul's representatives and to send a delegation to the South's upcoming Winter Olympics, which many see as a potential breakthrough in the standoff.
But Tillerson warned that more measures may be needed if North Korea continues its provocations, and Japan's Kono urged the allies not to let their guard down.
Without naming South Korea, Kono warned that Kim Jong-Un's regime "must be intending to drive a wedge between those tough countries and those that are not so tough."
For her part, Kang welcomed international support for sanctions, but her opening remarks carried a more optimistic message than those of her Japanese neighbor.
"I believe that the two tools, tough sanctions and pressure on the one hand and the offer of a different brighter future on the other, have worked hand in hand," she said.
"Indeed the concerted effort of the international community has begun to bear fruit," she explained.
Tillerson insisted after the talks that there is "no daylight" between Seoul and Washington on how to handle the crisis, and that the US-Japan-South Korea tripartite alliance remains "ironclad."
- 'Bark of a rabid dog' -
Moscow and Beijing were not represented in Vancouver and angrily dismissed the meeting.
"The most important relevant parties of the Korean peninsula issue haven't taken part in the meeting so I don't think the meeting is legal or representative," said Chinese foreign ministry spokesman Lu Kang.
Lu denounced the "Cold War mentality" of the United States, which is urging Beijing to cut off fuel oil supplies to Pyongyang -- a step too far for Beijing, which fears the collapse of Kim's regime more than its surrender.
Trans-Pacific tensions have been running high for months, despite the recent return to direct talks between Kim's regime and Moon Jae-In's South Korea.
As the talks got under way, Pyongyang responded to Trump's recent twitter warning that his nuclear arsenal dwarfs the North's fledgling missile batteries.
Official party newspaper Rodong Sinmun dismissed Trump's "swaggering" as the "spasm of a lunatic" frightened by North Korea's power and the "bark of a rabid dog."