The committee could also refer the matter to the General Assembly. Whether Iran would win a majority of votes among the membership would remain to be seen. Even if a majority sided with Iran, there is no expectation that the United States would rescind the decision.

Image Hamid Aboutalebi Credit... Mohammad Berno/Office of the Iranian President, via Associated Press

“What would they expect the U.S. government to do — say, ‘O.K., we were kidding’ ?” said Alireza Nader, an Iran expert at the Washington offices of the RAND Corporation. He said Iran would be better off to “just let it drop quietly.”

Mr. Ban’s spokesman, Stéphane Dujarric, declined to speculate on what might happen next. “We’ll have to wait and see what the committee does and what the committee decides,” he told reporters.

Iran’s basic argument is that the United States has violated the Headquarters Agreement signed when it agreed to host the world body in New York. The 1947 agreement obliges the host to allow access to foreign diplomatic representatives, even from countries the United States dislikes. But the United States also enacted a law that year to carry out the agreement, in which the host reserved the right to “safeguard its own security” by denying visas to foreign visitors to the United Nations deemed to be a threat.

Larry D. Johnson, an adjunct professor at Columbia Law School who was the United Nations deputy legal counsel from 2006 to 2008, said numerous clashes ensued over the years between the organization and host over the visa issue. Eventually, he said, the United States and United Nations came to an understanding that if the United States objected to a diplomat’s visa application, the United Nations would inform officials of that diplomat’s government, and “it’s up to them to decide to make a fuss or challenge or not.”

Mr. Johnson said that “supposedly many times the other country doesn’t insist and it goes away quietly — none of this is publicized. And sometimes the U.S. delays issuing the visa until it’s too late.”

In a 1988 case, when the United States denied a visa to Yasir Arafat, leader of the Palestine Liberation Organization at the time, the United Nations meeting was moved from New York to Geneva.