The United States has barred Iranian foreign minister Javad Zarif from traveling to the United States to attend a United Nations meeting on Thursday. While the United States government broadly has the authority to deny visas to foreign dignitaries to enter the United States, there has always been a carveout for diplomats on official business at the United Nations. This is enshrined in a 1947 agreement that established UN headquarters in New York. Known as the “headquarters agreement” the United States pledged to allow the travel of foreign diplomats to the UN, even if their movement outside of the United Nations is highly circumscribed.

But the Trump administration now seems to denying Zarif a visa to attend a Security Council meeting on Thursday — one that was scheduled before the recent escalation of tensions between the United States and Iran. The State Department claims that it did not have time to process his application. And in an interview, Zarif said that all things considered, he was glad to not travel to the United States at a time of escalating tensions between Iran and the US.

This episode highlights one important aspect of the relationship between the United Nations and the United States. As the host country of the UN, the United States holds some additional responsibilities with regards to the UN — and those additional responsibilities carry some important benefits to the United States.

Having the United Nations Headquartered in New York  is Broadly Beneficial to the United States

The United Nations was born American.  The idea of the modern UN was generated at a conference at Dumbarton Oaks in Washington, DC in 1944. The Treaty that brought the United Nations to life was signed in San Francisco in 1945. And since 1952, the United Nations has been headquartered in New York City, in its current location in the Turtle Bay neighborhood.

Since then, the Americanness of the United Nations has benefited the United States in ways big and small. From a transactional point of view, having the United Nations headquartered in the United States has helped American businesses. Some $1.7 billion worth of contracts are awarded to American companies from the United Nations each year. About half a billion of these contracts go to companies in New York alone.

Also, having the UN in New York has historically conferred a home field advantage for American diplomats. This includes well reported incidents of US spying on foreign diplomats; but also more broadly the ability of the US to leverage is soft power. This includes foreign diplomats sending their children to school in New York, and generally exposing to all all who visit the UN the pluralism and dynamism of New York City. The city is a a showcase for American diversity.

The privilege of hosting the UN also comes with responsibilities. This includes, above all else, allowing foreign diplomats — even of countries at which the United States is in conflict — to come to the United States to conduct diplomacy. Denying Javad Zarif a visa to attend a United Nations meeting undermines global confidence in the United States as acting as a steward of the UN.

In the near term, denying an Iranian diplomat entry to the UN undermines its place as a platform to conduct the kind of diplomacy that might prevent war. In the long term denying visas to foreign diplomats could trigger doubts around the UN about the United States’ commitment to the headquarters agreement. That would be bad for the UN — and for the US.