The Iranian flag waves outside of the UN building that hosts the International Atomic Energy Agency in Vienna, Austria. Picture: Ronald Zak/AP

New York  - The United Nations has voiced concerns to the United States over restrictions placed on Iranian Foreign Minister Mohammad Javad Zarif during his current trip to New York, UN spokesman Farhan Haq said on Monday.

Zarif arrived in New York on Sunday and plans to participate in a meeting on Wednesday as part of the UN's Economic and Social Council (ECOSOC) conference.

New restrictions effectively mean Iranian officials can only travel within a six-block radius of the United Nations, as of July 13, according to a State Department official.

This means Zarif is only allowed to travel between UN headquarters, the Iranian Mission to the UN and the residence of Iran's UN ambassador with an exception for travel to John F Kennedy Airport.

The US sees no reason for Iranian diplomats to be "freely roaming" around New York and "takes its obligations as the host of the United Nations seriously," the State Department official added.

Haq said the UN is in close contact with the US and Iranian missions regarding the matter and has conveyed its concerns to the US.

In recent weeks there has been a sharp increase in tensions between the US and Iran, including allegations that forces allied with Tehran targeted tankers at sea and the recent Iranian downing of a US drone.

Iran has also begun to incrementally violate the nuclear deal, with two recent breaches.

No meetings with US counterparts were announced, but rumours swirled in Tehran that Zarif planned to lay the groundwork for a potential meeting with American officials on the sidelines of the UN General Assembly in September.