It also requires countries to tell the United Nations how much North Korean coal they are buying and expands the list of banned items for import by North Korea, including luxury goods like bone china worth more than $100 as well as equipment with dual-use purposes.

The measure also urges countries to allow North Korean diplomatic missions around the world to have only one bank account. That, the United States says, is intended to limit the country’s penchant for using its envoys and embassies to further its nuclear program.

How successful the new measures will be, of course, depends on the willingness of countries to abide by them.

The United Nations secretary general, Ban Ki-moon, called the measures the “toughest” sanctions imposed by the Council. But he warned that the passage alone would be insufficient. “It is incumbent on all member states of the United Nations to make every effort to ensure that these sanctions are fully implemented,” he said.

The bigger uncertainty is what posture Mr. Trump will take toward North Korea and Mr. Kim — and, by extension, toward Beijing.

“If you look at North Korea, this guy, I mean, he’s like a maniac, O.K.?” Mr. Trump said at a campaign rally in January. He went on to say that “he really does have missiles, and he really does have nukes.” Since then, Mr. Trump and his transition team are likely to have been briefed on the nature and scope of North Korea’s nuclear arsenal.

American officials have warned for months that the North’s nuclear capabilities have increased sharply. Its missile and nuclear tests, the most recent in September, have accelerated, despite the imposition of sanctions in March.