TEHRAN, Iran (AP) — The United States notified Iran’s government on Tuesday that Tehran’s pick for a new U.N. envoy is “not viable,” a day after the U.S. Senate voted against letting the diplomat enter the country.

American officials objected to the selection of Hamid Abutalebi because of his alleged participation in a Muslim student group that held 52 Americans hostage for 444 days in the 1979 seizure of the U.S. Embassy in Tehran. The Obama administration has stopped short of saying it would refuse him a visa.