After months of soaring tensions, Foreign Minister Mohammad Javad Zarif came to New York for a UN session on sustainable development, where he denounced unilateral sanctions imposed by President Donald Trump.

Iranians are "subjected to the most brutal form of 'economic terrorism' -- deliberately targeting innocent civilians to achieve illegitimate political objectives," Zarif said from the rostrum.

The "unlawful, extraterritorial" sanctions "represent the greatest threat to the achievement of sustainable development goals of Iran and many of our neighbors," he said.

Trump last year withdrew from a multinational accord negotiated by his predecessor Barack Obama under which Iran drastically scaled back its nuclear program.

Trump, a staunch ally of Iran's rivals Saudi Arabia and Israel, instead imposed sweeping sanctions, including seeking to ban all Iranian oil exports in a bid to reduce the clerical regime's regional clout.

The United States, as the host country of the United Nations, heavily restricted Zarif, confining him to the blocks around the United Nations, the Iranian mission and the Iranian envoy's residence.

Zarif, speaking to reporters, said that the move was "certainly not a friendly action" and caused hardship for the families of mission workers.

"But for me it's fine because I don't have any work anywhere other than the three buildings," Zarif said.

A US-educated academic who speaks fluent English often sprinkled with idioms and humor, Zarif is widely seen as a moderate face of the Iranian government and in the past worked with Washington on issues from Afghanistan to the nuclear deal.

But Secretary of State Mike Pompeo said Wednesday that he believed that Iran's supreme leader, Ayatollah Ali Khamenei, was "calling all of the shots, 100 percent of them" on major strategic matters.

"Zarif comes around and talks about how he's the good guy. He has been the foreign minister while the Islamic Republic of Iran has taken every action we've seen and he is equally responsible for those activities," Pompeo told conservative radio host Hugh Hewitt.

The United Nations voiced concern over the restrictions imposed on Zarif by the United States, which under an agreement is required to facilitate diplomats' attendance for UN business.