The ambassador, Hamid Aboutalebi, was reportedly a member of a Muslim student group that held 52 Americans hostage for 444 days in the 1979 seizure of the US Embassy in Tehran.
Ministry spokeswoman Marzieh Afkham said today that Iran will consider subsequent actions once it receives an "official answer from official channels."
She acknowledged that after President Hassan Rouhani's nomination of Abutalebi, the ministry had communicated with "relevant US officials" but the envoy still hasn't been granted a visa for the US.