North Korea's leader, Kim Jong Un, "is begging for war," Nikki Haley, the U.S. ambassador to the United Nations, told the Security Council on Monday.

Her remark came a day after the North's most powerful nuclear test and hours after South Korean officials told lawmakers that North Korea might be preparing to launch another ballistic missile to mark the anniversary of the founding of the North's government in the coming days.

"We have kicked the can down the road long enough," Haley told the Council in an emergency meeting. "There is no more road left."

Haley did not threaten unilateral military action by Washington or repeat President Donald Trump's statement on Twitter that South Korea's call for more diplomacy was a form of "appeasement." She said instead that "the time has come for us to exhaust all of our diplomatic means before it's too late."

Last month, the council tightened­ sanctions against North Korea, unanimously adopting a resolution that Haley called "the most stringent set of sanctions on any country in a generation."

But since then, North Korea carried out one of its most provocative missile tests in recent years, hurling a ballistic missile directly over Japan that prompted the government in Tokyo to warn residents in its path to take cover.

And on Sunday, the North conducted its most powerful nuclear test ever, with a blast that experts said was far more destructive than the bombs that the United States dropped on the Japanese cities of Hiroshima and Nagasaki during World War II.

Koro Bessho, the Japanese ambassador to the United Nations, also stopped short of threatening imminent military action, but said the danger from North Korea had been "raised to an unprecedented level" and was "a grave threat to the peace and the security of the world."

Cho Tae-yul, the South Korean ambassador, described the North's latest test as "do-or-die behavior."

He called for "truly biting and robust measures that Pyongyang finds really painful," including blocking the flow of any money that might finance the North's weapons program.

François Delattre, the French ambassador, also called for new sanctions. "It is no longer a regional threat, it is a global threat," he said. "It is no longer a virtual threat, it is an imminent threat. It is no longer a serious threat, it is an existential threat."

Liu Jieyi, the Chinese ambassador, vowed that Beijing would "never allow chaos and war" on the Korean Peninsula, where the United States and China were both combatants in a conflict that lasted from 1950 to 1953. He called for all sides to return to the negotiating table, as did Vasily Nebenzya, the Russian ambassador.

The nuclear test that the North carried out on Sunday set off a magnitude 6.3 tremor centered at the testing site in the country's northeast, the U.S. Geological Survey said. It was followed by a weaker tremor believed to have resulted from a collapse in the testing site.

Trump said on Twitter that Sunday's test was an "embarrassment" to China, the North's biggest ally and trade partner. He also criticized South Korea, a U.S. ally, which he accused of "talk of appeasement."

Then on Monday, the South Korean military carried out drills, with F-15K fighter jets and ground forces firing missiles in a simulated attack on the North's nuclear site. The country's president, Moon Jae-in, talked with Trump by telephone on Monday, the South Korean leader's office said.

"President Trump reaffirmed the United States' ironclad commitment to defend South Korea," said Park Soo-hyun, a spokesman for Moon. "The two leaders also agreed to push for maximum pressure and sanctions against North Korea and a stronger sanctions resolution at the United Nations Security Council."

During the call, the spokesman said, Trump resolved a major South Korean grievance by agreeing to let it build more powerful non-nuclear ballistic missiles.

Under a treaty with the United States that was aimed at preventing a regional arms race, South Korea has been able to build ballistic missiles only with a range of up to 497 miles. Those missiles' payload were not allowed to exceed 500 kilograms, about half a ton.

On Monday, Trump agreed to lift the upper limit on the payload, Park said. Moon agreed to help the United States complete the deployment of a missile defense system, known as THAAD, as soon as possible.

Testifying before the National Assembly on Monday, Defense Minister Song Young-moo of South Korea said he had told his U.S. counterpart, Jim Mattis, in a meeting last week that the United States needed to send long-range bombers, aircraft carriers and other strategic assets to the Korean Peninsula more often or regularly to reassure the South Koreans.

He said he told Mattis that many in his country were calling for the reintroduction of U.S. tactical nuclear weapons to South Korea. He did not disclose how Mattis responded.