The U.S. is tightly limiting travel by Iranian officials visiting or assigned to the United Nations, sparking concern from the world body.

Representatives to the UN from Iran and some other countries have long had some limitations on their movements. But the new rules for Iranians — imposed as its foreign minister was preparing to arrive for UN meetings this week — are particularly strict.

Visiting officials, Iranian diplomats posted at the country's UN mission, and their families now can travel only among Kennedy airport and three places in Manhattan: the mission, the Iranian ambassador's residence and a six-block radius that includes the UN headquarters, according to a diplomatic note sent Saturday to Iranian officials and seen by The Associated Press.

The diplomats can seek waivers for housing or hotels, but it is not known whether waivers would be granted or whether they could apply to doctors' appointments, children's schooling or other activities.

The new rules come amid rising tensions between two longtime adversaries. It's not immediately clear whether the limitations are the tightest the U.S. has ever imposed, but they are far more restrictive than a previous policy that let Iranian representatives to the UN travel within a 40-kilometre radius of Columbus Circle in midtown Manhattan.

"It is certainly not a friendly action," Iranian Foreign Minister Mohammad Javad Zarif told reporters Wednesday at the UN.

He said that while he personally didn't need to go beyond the permitted places, the restrictions create "basically inhuman conditions" for the mission's diplomats and their families.

UN deputy spokesperson Farhan Haq said the organization had raised concerns with the U.S. and Iranian missions about the limitations.

"We'll continue to take up the matter as needed," he said.

The U.S. State Department said on Wednesday that the restrictions are "fully consistent with our obligations" as the UN's host country. "The U.S. intends to stick to its obligations."

U.S.-Iran tensions high

Tehran and Washington severed diplomatic ties after the 1979 Islamic Revolution in Iran and the hostage crisis that ensued when militant students stormed the U.S. Embassy.

Friction flared once again after U.S. President Donald Trump last year pulled the U.S. out of Iran's 2015 nuclear deal with world powers — a pact he called one-sided — and reimposed sanctions on Tehran's oil exports. The sanctions have exacerbated an economic crisis that has sent Iran's currency plummeting.

Iran recently began surpassing limits on the amount and purity of uranium it is allowed to stockpile under the nuclear agreement. Tehran has said the moves can be reversed if the deal's other participants come up with economic incentives that effectively offset the American sanctions.

An oil tanker is seen on fire in the Gulf of Oman on June 13 after two oil tankers near the Strait of Hormuz were reportedly attacked amid heightened tensions between Washington and Tehran. (ISNA/Associated Press)

The U.S. has sent thousands of troops, an aircraft carrier, nuclear-capable B-52 bombers and advanced fighter jets to the Middle East, and fears are growing of a wider conflict after mysterious attacks on oil tankers near the Strait of Hormuz blamed on Iran, attacks by Iranian-backed rebels in Yemen on Saudi Arabia and Iran's downing of a U.S. military drone.

The U.S. also imposes various travel restrictions on UN diplomats from China, Cuba, North Korea, Russia and Syria. The list has varied over the years, and countries have periodically chafed at the limitations.

Secretary of State Mike Pompeo told The Washington Post on Sunday that it is "absolutely appropriate" that Iran's foreign minister have the travel rights due under a longstanding U.S. agreement with the United Nations, but "nothing more than that."

"U.S. diplomats don't roam around Tehran, so we don't see any reason for Iranian diplomats to roam freely around New York City, either," he said.