Reuters - The United States has tightly restricted the travel of more than a dozen Iranian diplomats and their families living in New York, according to a U.S. diplomatic note to sent to the Iran mission to the United Nations and seen by Reuters on Tuesday.

The diplomats are subjected to the same rules imposed by the United States on Iran’s Foreign Minister Mohammad Javad Zarif, who arrived on Sunday amid heightened tensions between the two countries.

They may only travel between the United Nations, the Iranian U.N. mission, the Iranian U.N. ambassador’s residence and John F. Kennedy airport. There is also a carve out for the six blocks surrounding Queensboro Plaza in Long Island City in the borough of Queens. It was not immediately clear why.

Longtime U.S.-Iran strains have worsened since U.S. President Donald Trump last year quit a 2015 international agreement to curb Iran’s nuclear program in return for sanctions relief. Trump has imposed more sanctions on Iran.

Washington and Tehran sent mixed signals on Tuesday about resolving their disputes as Iran’s supreme leader threatened to further breach the nuclear deal while Trump cited “a lot of progress.”

The July 12 diplomatic note said the travel rules, which are open-ended, apply to “all members of the permanent mission of Iran to the United Nations, their immediate family members, and representatives of the Iranian government to the United Nations.”

It said a waiver would be required from U.S. State Department Office of Foreign Missions for any other travel and requests must be made at least five days in advance. The Iranian U.N. mission is also required to submit residential and hotel accommodations for approval.

The Iranian U.N. mission did not immediately respond to a request for comment. A spokesman for Iran’s foreign ministry said on Monday Zarif’s work in New York was unaffected.

The United Nations said on Monday that it told the United States it was concerned by the new tight travel restrictions. A U.S. State Department official said the United States had acted “in a manner that is fully consistent” with its obligations under a 1947 agreement with the United Nations.

Before the new rules, Iranian diplomats - like envoys of North Korea, Syria and Cuba - were already confined to a radius of 25 miles from Columbus Circle in Midtown Manhattan. According to the U.N. Blue Book, which lists diplomats of each mission to the world body, there are 13 Iranian diplomats in New York.

Under the 1947 U.N. “headquarters agreement,” the United States is generally required to allow access to the United Nations for foreign diplomats. But Washington says it can deny visas for “security, terrorism, and foreign policy” reasons.

The U.S. diplomatic note said Zarif was “being admitted to the United States for the sole purpose of attending U.N. meetings” and that “he should restrict his activities to U.N.-related business only.

Zarif is due to attend a ministerial meeting at the U.N. on Wednesday on sustainable development goals, which aim to tackle issues including conflict, hunger, equality and climate change by 2030. On Monday, he did interviews with British and U.S. media at the residence of the Iranian U.N. ambassador.