Iran has formally protested Washington's refusal to grant a visa to its new UN ambassador, saying the move damages international diplomacy and sets a "dangerous" precedent

The U.S. State Department and White House have said that Iran's selection of Hamid Aboutalebi to be its United Nations envoy is not acceptable. Aboutalebi was a member of the group responsible for the 1979 takeover of the U.S. Embassy in Tehran that held 52 Americans hostage for 444 days. Aboutalebi has insisted his involvement in the group was limited to translation and negotiation.

Iran's UN Mission sent a letter to the UN's Committee on Relations with the Host Country and released a copy of it Monday night. The committee can hold a hearing on the issue but cannot change the U.S. decision.

Iran's letter said the United States was breaching its obligations under the U.S.-UN Host Country Agreement, which is a treaty and U.S. law that generally requires the host country to allow access to diplomats and UN guest speakers.

"The Agreement has unambiguously stated that its provisions shall be 'applicable irrespective of the relations existing between the Governments of the persons referred to in that section and the Government of the United States,"' the Iranian letter said.

"This decision of the U.S. Government has indeed negative implications for multilateral diplomacy and will create a dangerous precedence and affect adversely the work of intergovernmental organizations and activities of their Member-States," said the Iranian letter to the committee and to Secretary-General Ban Ki-moon.

The United States has said there are loopholes in the agreement that allow it to refuse a visa to people considered a danger to the United States, or who have been involved in terrorist activities.

State Department spokeswoman Jen Psaki on Tuesday reiterated that the U.S. deems Aboutalebi's nomination "unacceptable."

"And while we're not going to get into any specifics of what we do or don't think he was involved in during the hostage crisis, he himself has said he was involved, and given his role in the events of 1979, which clearly matter profoundly to the American people, it would be unacceptable for the United States to grant this visa," Psaki said.

A new law passed last week by Congress, but so far not signed by President Barack Obama, would bar Aboutalebi on the grounds of his alleged terrorist connections.

In 1988 the United States refused PLO chairman Yasser Arafat a visa to speak at the General Assembly, in part citing as precedent its refusal of visas throughout the 1980s to proposed Iranian diplomats who were linked to the UN Embassy takeover.