In a flurry of phone calls with world leaders, president Donald Trump took a tough line against negotiating with North Korea as the communist country's latest nuclear test exposed stark differences among international leaders for containing the threat.
The US president stressed "now is not the time to talk to North Korea" and that "all options remain open to defend the United States and its allies", according to a White House description of his telephone call with British prime minister Theresa May on Tuesday.
The readout was released shortly before Mr Trump was to speak with Chinese president Xi Jinping, whose opinion is critical for getting the UN to apply tighter sanctions on North Korea, including possibly restricting China's oil sales to its unpredictable neighbour.
Mr Trump also discussed North Korea's purported hydrogen bomb test with Australian prime minister Malcolm Turnbull.
The weekend explosion was Pyongyang's strongest-ever nuclear test and follows launches in July of an intercontinental ballistic missile that could reach the US mainland.
Mr Trump and Mr Turnbull "confirmed that their two countries will intensify joint efforts to denuclearise North Korea".
While Mr Trump consulted his international counterparts, defence secretary Jim Mattis, secretary of state Rex Tillerson and director of National Intelligence Dan Coats planned to hold closed-door briefings for House and Senate members on the North Korean threat.
Mr Mattis has reaffirmed Washington's commitment to defend its South Korean ally, warning once more that any North Korean threat would trigger an "overwhelming" response, the Pentagon said on Wednesday.
In a conversation with South Korean defence minister Song Young-moo on Tuesday to address North Korea's latest and most powerful nuclear test to date, Mr Mattis said the US "remains ironclad in its commitment to the defence of" South Korea.
"He further emphasised that any threat to the United States, its territories, or its allies will be met with a massive, effective, and overwhelming military response," Pentagon spokeswoman Dana White said.
As the Trump administration looked for partners to increase the North's economic and diplomatic pressure, Russian president Vladimir Putin was pushing in the opposite direction. He warned against cornering Pyongyang, a sentiment likely to be shared by Beijing, which fears a North Korean collapse on its border.
Mr Putin said the nuclear test "flagrantly violates" international law but called for talks with North Korea, saying sanctions are not a solution.
Speaking after a meeting on Wednesday with the South Korean president, Mr Putin urged support for a Russian-Chinese roadmap that seeks a North Korean nuclear freeze in exchange for the US and South Korea curbing military drills. Washington rejects the proposal; Mr Putin insisted it "offers a genuine way to defuse the tensions and a step-by-step settlement".
"We should not give in to emotions and push Pyongyang into a corner," Mr Putin said. "As never before everyone should show restraint and refrain from steps leading to escalation and tensions."
Mr Moon urged Russia to back stronger sanctions on the North, including an oil cutoff, but Mr Putin worried that such moves would hurt North Korea's people, said Yoon Young-chan, Mr Moon's chief press secretary.
Mr Moon also called for a ban on overseas North Korean workers — many of them in China and Russia — who provide foreign currency to the North.
A liberal who took office in May, the South Korean leader initially advocated a diplomatic approach on North Korea. His government has taken a harder stance as the North continued its torrid pace of weapons tests, and Mr Moon said on Tuesday he believes now is not the time for talks and that the international community must increase the pressure on North Korea.
Illustrating the country's hardening sentiment, South Korea says the US military will begin adding more launchers to a contentious high-tech US missile defence system in South Korea on Thursday. Although focused on deterring North Korea, China and Russia see the system as harmful to their security interests.
