Iran has no plans to name a new diplomat to the United Nations, its foreign ministry said on Saturday, after the US blocked its pick in a rare rebuke that could stir fresh animosity at a time when the two countries have been seeking a thaw in relations.

The Obama administration said on Friday the US had informed Iran it would not grant a visa to Hamid Aboutalebi, a member of the group responsible for the 1979 takeover of the US embassy in Tehran. While US officials had been trying to persuade Iran to simply withdraw Aboutalebi's name, the announcement amounted to an acknowledgement that those efforts had not been successful.

"The ministry of foreign affairs is pursuing this issue through anticipated legal channels at the UN," the deputy foreign minister, Abbas Araghchi, was quoted as saying by Iran's semi-official Mehr news agency. "We have no choice to substitute Mr Aboutalebi."

Aboutalebi is alleged to have participated in a Muslim student group that held 52 Americans hostage for 444 days during the embassy takeover. He has insisted his involvement in the group Muslim Students Following the Imam's Line was limited to translation and negotiation. Iran says he is one of the country's best diplomats, and that he previously received a US visa. He has already served at Iranian diplomatic missions in Australia, Belgium and Italy.

Hamid Babaei, a spokesman for the Iranian UN Mission, on Friday said the decision was not only regrettable but "in contravention of international law, the obligation of the host country and the inherent right of sovereign member states to designate their representatives to the United Nations".

As host country for the UN, the US must provide rights to persons invited to the New York headquarters. However, exceptions can be made when a visa applicant is found to have engaged in spying against the US or poses a threat to American national security.

Denying visas to UN ambassadorial nominees or to foreign heads of state who want to attend UN events in the US is extremely rare, though there appears to be precedent. According to a paper published by the Yale Law School, the US rejected several Iranians appointed to the UN in the 1980s who had played roles in the embassy hostage crisis or other acts against American citizens. In 1988 the US denied a visa to the Palestinian leader Yasser Arafat, preventing him from speaking at the UN.



Iran's choice of Aboutalebi had pinned President Barack Obama between congressional pressure to deny the envoy entry into the US and the White House's delicate diplomatic dealings with Tehran. After more than three decades of discord, US and Iranian officials have started having occasional direct contact, including a phone call last fall between Obama and the new Iranian president, Hassan Rouhani.

The US and its international partners have also reached an interim agreement with Iran to halt progress on Tehran's disputed nuclear programme. Officials are in the midst of negotiating a long-term agreement that seeks to eliminate concerns that Iran may use its nuclear capabilities to build a nuclear weapon.