The White House has refused to issue a US visa to Iran's next UN ambassador, who was involved in the seizure of the US embassy in Tehran in 1979 when 52 Americans were held for 444 days.
The decision in effect bars Hamid Aboutalebi from taking up the role at the UN in New York.
The BBC reports the movie is unprecedented. The United States has never before denied a visa for a UN ambassador.
President Barack Obama was under intense pressure from the US Congress not to allow him to enter the country.
The House of Representatives and the Senate both unanimously voted in favour of a bill barring Mr Aboutalebi from the United States. It still requires the signature of the president before it can become law.
Iran says Mr Aboutalebi is one of its most experienced diplomats and stands by his nomination.
White House spokesman Jay Carney said on Friday the UN and Iran had been told a visa will not be issued to Mr Aboutalebi. He said the president shared the sentiments of Congress.
In an interview with an Iranian news site last month, Mr Aboutalebi said he was not part of the group that took over the US embassy and was only later asked to translate for the students.