Some U.S. allies appeared to blame Trump's remarks for the escalation. Germany's foreign office called “on all parties for moderation,” on Wednesday.
“Sabre-rattling won't help,” the foreign ministry said in the tweet.
Concerns in Germany were shared by officials and experts elsewhere.
The spokeswoman for the European Union's foreign policy chief agreed that “a lasting peace and denuclearization of the Korean Peninsula must be achieved through peaceful means.”
“That excludes military action,” the spokeswoman said.
In New Zealand, Prime Minister Bill English similarly called Trump’s comments “not helpful” in a standoff that was already “very tense.”
Australian Prime Minister Malcolm Turnbull warned that responding to North Korea's threats with “fire and fury,” as Trump had threatened, would have “catastrophic consequences” worldwide. The Australian leader argued that instead, economic pressure and sanctions could be more effective at deterring the regime.
Turnbull was referring to sanctions passed unanimously by the U.N. Security Council last weekend — a response to North Korea's launch of two intercontinental missiles in July. The latest measures step up restrictions on North Korea's international trade, with estimates saying that they may cost the country about $1 billion annually.
“The global community, led by the Security Council, including China and Russia, are all united in seeking to bring the maximum economic pressure on North Korea to bring them to their senses without conflict,” Turnbull was quoted as saying Wednesday.
“A conflict would be shattering. It would have catastrophic consequences. We all understand that,” Turnbull said.
During a speech to commemorate the victims of the World War II atomic attack on the Japanese city of Nagasaki, the city's mayor lashed out at world leaders on Wednesday, saying that "the nuclear threat will not end as long as nations continue to claim that nuclear weapons are essential for their national security." Nagasaki was hit by an atomic bomb on Aug. 9, 1945. It is estimated that as many as 75,000 people were killed.
Amid such sobering warnings echoing the lessons of history, some nations worried that Trump's threats could endanger the prospects of recent concerted international efforts to prevent more nuclear weapons attacks. A statement released by China's foreign ministry warned all parties to avoid actions and rhetoric that could contribute to an escalation, and it urged more emphasis on international talks instead, according to Reuters.
Sacha Sergio Llorenty Soliz, the U.N. ambassador of Bolivia, which is currently a temporary member of the Security Council, said that Trump's escalation of rhetoric “goes against the spirit” of the U.N. sanctions, which called for international talks. Trump's decision to raise tensions would be “detrimental” to international peace, Soliz said.
But representatives for Britain and for NATO refrained from criticizing Trump. Speaking to reporters in New York, Matthew Rycroft, Britain's U.N. ambassador, said the United Kingdom was standing “shoulder to shoulder with the United States.”
Asked about the rhetoric used by Trump on Tuesday, Rycroft responded: "[What's] hurting the six-party talks is the inability so far of the North Korean regime to do what it has to do, which is to halt its nuclear program and to halt its intercontinental ballistic missile program.”
NATO spokesman Dylan P. White said the organization was “concerned by North Korea's pattern of inflammatory and threatening rhetoric.”
“We call on North Korea to refrain from further provocations,” White said.