“We’re going to be generous to those that share our values, generous to those who want to work with us,” she said, “and not those that try and stop the United States, saying they hate America and are counterproductive for what we’re doing.”

That tone has been matched by action over the last year as the United States has pulled out of one United Nations body after another.

Just weeks after Mr. Trump’s first speech before the General Assembly he withdrew the United States from Unesco, the United Nations cultural organization. This summer, the United States left the Human Rights Council, revoked funding for the United Nations agency that provides education and health care to Palestinians classified as refugees, and boycotted a United Nations agreement on migration.

Mr. Trump’s decisions to quit the Paris climate accord and the Iran nuclear deal are still sources of deep bitterness, particularly among close allies. His elevation of John R. Bolton, who muses about defunding the United Nations, to national security adviser was greeted with a shudder.

At a news conference last Thursday, the United Nations secretary general, António Guterres, said that multilateralism was “under attack from many directions,” but diplomatically sidestepped a question about whether he thought Mr. Trump was a direct threat.

“I don’t like to personalize things,” he said.

Others were more blunt.

“It’s not just stepping back,” said Louis Charbonneau, the United Nations director for Human Rights Watch. “It’s an assault on the most important institutions we have for accountability and monitoring and exposing the worst abuses.”