“President Trump has used just about every lever you can use, short of starving the people of North Korea to death, to change their behavior,” Mr. Bossert said. “And so we don’t have a lot of room left here to apply pressure to change their behavior.”
In fact, the public C.I.A. assessment is that no amount of economic sanctions will force the North to give up its nuclear program.
The United States, which has led the sanctions effort at the Security Council, drafted the latest round of sanctions in consultation with other members, most notably China, which historically has been reticent to impose them. The deadline for the return of North Korean workers was changed to 24 months from 12 months, partly in response to Chinese and Russian concerns.
It was a striking display of unity, only a day after most members of the United Nations General Assembly condemned the new United States stance on Jerusalem.
Nikki R. Haley, the American ambassador, thanked the other council members — especially China — for coming together on the resolution and said further North Korean defiance would “invite further punishment and isolation.”
Ms. Haley called North Korea’s intercontinental ballistic missile test last month “another attempt by the Kim regime to masquerade as a great power while their people starve and their soldiers defect.”
Speaking to reporters before the meeting, Matthew Rycroft, the British ambassador, said the ability of all council members to come together on the North Korea issue showed they are “seeing the bigger interests we all have.”
Mr. Rycroft said the new measures “tighten the grip and make it even harder for the regime to fund the illegal programs, and at the same time insure we don’t make life harder for the poor people of North Korea.”
The assent of China and Russia to the tightened measures appeared to reflect the growing impatience with North Korea by the world’s most powerful nations, regardless of their politics.
Experts on North Korea said the new measures had the potential to dissuade Mr. Kim from further escalating the tensions with more tests, but were cautious about predicting his behavior.
“If the international community, including countries like China and Russia, implements these measures fully, faithfully and quickly, it will apply an unprecedented and irresistible level of pressure on the North Korean regime,” said Evans J.R. Revere, a former senior State Department diplomat for East Asia.
If that happens, he said, it would force North Korea “to make a choice between continued defiance of the international community on the one hand and a return to the negotiating table on the other.”
Under North Korea’s young leader, Kim Jong-un, grandson of its founding father Kim Il-sung, the impoverished country of 25 million has exalted nuclear weapons and threatened to use them against the United States, its No. 1 perceived enemy since an armistice halted the Korean War more than six decades ago.
President Trump has responded to these threats by vowing to “totally destroy” North Korea if attacked and pressing China, North Korea’s most important trading partner, to cut off oil exports to the country.
There have been mixed signs, at best, that diplomatic efforts to avert a military confrontation are working.
Last week Secretary of State Rex W. Tillerson told the Security Council that “a sustained cessation of North Korea’s threatening behavior must occur before talks can begin,” a sharp contrast from conciliatory comments he had made just a few days earlier.
The North Koreans have conducted six nuclear tests and have demonstrated major progress with their missiles even though the United Nations has prohibited them.
The tightened measures approved on Friday included a restriction that would cut the supply of North Korea’s imports of refined petroleum by roughly 90 percent. The would also place limits on crude oil deliveries and give other countries enhanced powers to stop North Korea-bound ships suspected of carrying contraband.
A further punitive action requires North Korea to recall thousands of North Korean laborers, many of them working in Russia and China, who send remittances home, an important source of government income. That action tightens an earlier sanction that banned North Korea from sending more workers abroad.
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