"Given his role in the events of 1979, which clearly matter profoundly to the American people, it would be unacceptable to grant this visa," State Department spokeswoman Jen Psaki said on Tuesday.

Washington has decided to deny visa to Aboutalebi over his alleged involvement in the takeover of the US Embassy in Tehran during post-revolution incidents in 1979.

On April 10, the US House of Representatives unanimously approved a legislation that prevents Aboutalebi from entering the US.

Iran has rejected the US decision as unacceptable and says it will follow up on the issue through diplomatic channels at the UN.

Iran says the US has violated international law as well as an agreement between the UN and Washington.

"The official mechanisms for lodging the complaint at the United Nations have been activated, and are under way," Iran’s Foreign Ministry spokeswoman Marziyeh Afkham said on Monday.

On November 4, 1979, a group of Iranian university students took over the US Embassy in Tehran, which they believed had turned into a "den of espionage". Documents found at the compound later corroborated the claims by the students.

The UN regulations stipulate that each country is allowed to select its own representatives at the international organization and the US, as the host country, must grant visas to the appointed diplomats.

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