(CNN) -- The United States has told Iran that it will not issue a visa to Hamid Aboutalebi, the Islamic republic's choice for ambassador to the United Nations, the White House says.
Press secretary Jay Carney made the announcement at Friday's White House briefing.
The United States opposes the appointment of Aboutalebi because of his ties to the 1979 takeover of the U.S. Embassy in Tehran. The White House is also still reviewing a bill passed in Congress this week prohibiting the ambassador from entering the United States.
Aboutalebi was a member of the Muslim Students Following the Imam's Line, the group of militants who seized the embassy on November 4, 1979, holding 52 Americans hostage for 444 days.
He is a veteran diplomat who has served as Iran's ambassador to Australia, Belgium, Italy and the European Union. He has also held high-profile posts in the Iranian Foreign Ministry. He currently works in the political affairs office of President Hassan Rouhani and is believed to be close to the Iranian leader, who is widely viewed as a moderate with a reformist agenda.
In an interview with Iranian media, Aboutalebi said he served as translator and negotiator, but denied taking part in the initial occupation of the embassy.
One of the leaders of the takeover of the U.S. Embassy, Abbas Abdi, told CNN exclusively from Tehran that "Mr. Aboutalebi was not in Tehran during the initial invasion."
Abdi, currently a reformist journalist, said Aboutalebi has "no relation to the decision-making team, the group who invaded and those who continued the hostage captivity in Iran."
The choice of Aboutalebi could complicate President Barack Obama's efforts to re-engage with Tehran after the election of Rouhani and negotiate a comprehensive agreement with five other world powers to curb Iran's nuclear program.
With no formal relations between the United States and Iran, the Iranian mission to the United Nations is Tehran's only diplomatic operation in the United States and has played a role in facilitating unofficial exchanges of messages between the two nations.
The step is unusual, given that the United States is obligated to grant entry visas to representatives of U.N. member states, in accordance with a 1947 agreement signed with the world body.
Last year, Sudanese President Omar al-Bashir decided not to attend the U.N. General Assembly when the State Department failed to respond to his visa application. The International Criminal Court has issued warrants for Bashir's arrest and referral for trial in The Hague for alleged crimes against humanity.
Although the United States is not a party to the court, the ICC has asked the United States to surrender him if he enters American territory.
Even if the United States granted Aboutalebi a visa, he would not be free to move about the country. As a representative of a country listed as a state sponsor of terrorism by the State Department, Aboutalebi would be confined to a radius of 25 miles from Manhattan, just as diplomats from North Korea and Syria are.
Still, former American hostage Barry Rosen said it would be a "disgrace" if Washington gave a visa to Aboutalebi, and he called on the Obama administration to deny his application.
"It may be a precedent but if the President and the Congress don't condemn this act by the Islamic Republic, then our captivity and suffering for 444 days at the hands of Iran was for nothing," he said in a prepared statement. "He can never set foot on American soil."
CNN's Tara Kangarlou contributed to this report.