The United States says it has voiced concern to Iran on its potential selection of a UN ambassador with alleged links to the 1979 seizure of the US embassy.
Iran has not announced a nominee to be its ambassador in the United Nations. But a US senator critical of US outreach to Iran said that the Islamic republic has sought a visa for Hamid Aboutalebi, who joined a student group behind the hostage-taking.
"The US has raised it with the Iranian government, our concerns about this," State Department deputy spokeswoman Marie Harf told reporters.
She declined further details on Thursday but said previously that Aboutalebi's nomination would be "extremely troubling."
As the host government, the United States generally is obliged to issue visas to diplomats who serve at the United Nations, although Harf said there were "certain circumstances" for exceptions.
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Aboutalebi is a career diplomat considered close to Iranian reformists including President Hassan Rouhani, who swept to power last year in part on pledges to ease tensions with the West.
Aboutalebi has insisted he was not part of the hostage-taking in November 1979, when students who had overthrown the pro-Western shah seized the US embassy, but that he later joined the student group.
He has said that he worked as a translator when the students, soon after the hostage taking, released 13 women and African Americans to highlight what they said was Islamic respect for women and poor US treatment of minorities.
The remaining 52 diplomats spent a total of 444 days in captivity, enraging the United States.
The two countries still do not have diplomatic relations, but Rouhani and US President Barack Obama have taken steps to ease tensions through a tentative agreement to freeze parts of Iran's nuclear program.
