The effort, which senior administration officials described as a last best chance to resolve the standoff with the North using sanctions rather than military means, came as South Korean officials said Monday that they had seen evidence that North Korea may be preparing another test, likely of an intercontinental ballistic missile.
That test, which would be the nation’s third in a month, could be timed to mark the anniversary of the founding of North Korea by Kim Il-sung, the grandfather of the current leader. It is unclear where the test might be aimed, but Pentagon officials said they were examining options in case it was meant to demonstrate that the North could put a missile, with accuracy, off the coast of Guam, an American territory.
The call for the fuel cutoff, which is expected to be part of a draft resolution that the United States is beginning to discuss privately with other members of the Security Council, came a day after North Korea’s most powerful nuclear test in the 11 years it has been detonating nuclear weapons.
It is far from clear that China’s president, Xi Jinping, would be willing to go along with the highly aggressive step of cutting off fuel to the North. Roughly 90 percent of North Korea’s trade, and nearly all of its imported energy supplies, come from China. China’s overall trade with the North was up significantly in the past 12 months, and it has long feared that an oil cutoff would lead to the collapse of the regime.
That, in China’s eyes, would only invite South Korea to take over the North, and put an American ally on China’s border.
The subject of fuel cutoff is likely to come up in a phone call with President Xi that the White House was trying to arrange.
Speaking to the Security Council in an emergency session on Monday, Nikki R. Haley, the American ambassador to the United Nations, said North Korea’s leader, Kim Jong-un, “is begging for war.”
“We have kicked the can down the road long enough,” Ms. Haley told the council in an emergency meeting. “There is no more road left.”
Ms. Haley did not threaten unilateral military action by Washington or repeat the president’s statement on Twitter that South Korea’s effort to engage the North directly 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.”
Even as Ms. Haley called for more diplomacy, Mr. Trump agreed in a phone call on Monday evening with South Korea’s president, Moon Jae-in, to allow South Korea to build more powerful non-nuclear ballistic missiles, said Park Soo-hyun, a spokesman for Mr. Moon. While the South has pressed for such permission for many years, the change is unlikely to alter the strategic balance on the Korean Peninsula.
“President Trump reaffirmed the United States’ ironclad commitment to defend South Korea,” Mr. Park said. “The two leaders also agreed to push for maximum pressure and sanctions against North Korea.”
Inside the White House, there is little expectation that the drive to cut off North Korea’s fuel — which echoes the energy embargo that the United States used to try to force Japan to change its behavior in 1941, before the attack on Pearl Harbor — will work because of the Chinese reluctance to take that step.
Nonetheless, fuel-related sanctions are the focus of the Trump administration’s latest efforts at the Security Council, according to the senior American officials.
Ms. Haley’s comments on Monday were notable in part because while they called for a last stab at diplomacy, they also ruled out the one diplomatic option considered the most viable first step — a Chinese and Russian proposal for a “freeze” on the North’s nuclear and missile testing in return for some kind of freeze on United States military exercises.
She said that at a time that the North was threatening the United States, it would be unwise to trim back training with allies.
“There are some good reasons for not doing a freeze-for-freeze,” said Richard N. Haass, the president of the Council on Foreign Relations, and a former senior diplomat in both Bush administrations. “But that doesn’t mean no freeze for something. The U.S. has not put forward our own options, what we would be prepared to sign up for. There’s a diplomatic vacuum.”
As Mr. Trump considered his options, however, he is also confronting the implications of some of his own rhetoric.
He declared that North Korea would not be permitted to fire I.C.B.M.’s — “It won’t happen!” he tweeted on Jan. 2 — and they were fired. He said the United States would bring “fire and fury” to the North if it was threatened, and Sunday’s nuclear test, claimed by the North to be a hydrogen bomb, was accompanied by North Korea’s announcement that the weapon could be fitted on a missile that could reach the United States.
In short, Mr. Trump has run the risk of doing what he charged President Barack Obama with doing in Syria: drawing a line and not enforcing it.
His senior aides say that it is too early to make that judgment, and that a combination of crushing economic pressure and stepped-up military patrols, missile defenses and practice bombing runs may eventually change Kim Jong-un’s behavior.
The president’s only declared line, they argue, is that he will never allow the United States to be under the threat of a nuclear attack by the North.
So far, intelligence agencies have stopped short of formally assessing that the North has all the elements it needs to reach the United States with a weapon. But if it is missing some elements – including the ability to protect a warhead from burning up during the stresses of re-entering the atmosphere – it seems likely to achieve them soon.
Monday’s meeting of the Security Council was the second time in less than a week that the most powerful body of the United Nations had met to discuss North Korea, and the tenth time it has done so this year.
Last month, the council tightened sanctions against North Korea, unanimously adopting a resolution that Ms. 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 Sunday’s test was the most powerful yet, 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.
In her remarks, Ms. Haley gave a lengthy summary of the North’s flouting of international law since 1993, when the United Nations urged the country to reconsider its decision to withdraw from the Nuclear Nonproliferation Treaty. The North’s moves the following year triggered a crisis similar to today’s, and was the closest the United States and North Korea have come to resuming the Korean War.
“Despite our efforts over the past 24 years, the North Korean nuclear program is more advanced and more dangerous than ever,” she said. “They now fire missiles over Japanese airspace.”
“They now have I.C.B.M. capabilities,” she said, referring to intercontinental ballistic missiles. “They now claim to have tested a hydrogen bomb. And just this morning there are reports that the regime is preparing for yet another I.C.B.M. launch.”
“We have taken an incremental approach,” Ms. Haley added, “and despite the best of intentions, it has not worked.”
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.”
While Japan and South Korea joined the condemnations, there are clear tensions. Mr. Trump’s jab at the South on Sunday that it was practicing “appeasement” generated headlines in Seoul, as did Mr. Trump’s threat to scrap a free trade agreement with South Korea, one that was signed in part to demonstrate strategic unity.
There are clear divisions in South Korea about how to deter the North.
Testifying before the National Assembly on Monday, Defense Minister Song Young-moo of South Korea said he had told his American 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 had told Mr. Mattis that many in his country were calling for the reintroduction of American tactical nuclear weapons to South Korea. He did not disclose how Mr. Mattis responded.
Those weapons were removed from the South by the United States more than 25 years ago.
Mr. Moon’s office said his government remained opposed to the reintroduction of American tactical nuclear weapons to South Korea, saying that doing so would make it more difficult to persuade North Korea to give up its own nuclear weapons.
David E. Sanger reported from Washington and Choe Sang-Hun from Seoul, South Korea. Sewell Chan contributed reporting from London; Austin Ramzy and Gerry Doyle from Hong Kong; and Somini Sengupta from New York.