Tehran, April 14 (IANS): The Iranian parliament has given a 10-day ultimatum to the government to file a lawsuit against the US for denying visa to Iran's UN envoy-designate, an official said Monday.

"The official mechanisms for following up the case have been activated, and are underway," Press TV quoted Iran's Foreign Ministry Spokeswoman Marzieh Afkham as saying.

The US's decision not to issue a visa for Hamid Aboutalebi is a breach of international treaties, and runs contrary to the agreement between the UN and the US government, Afkham said.

"Tehran can follow up on the issue through the UN Secretariat and contact UN Secretary-General Ban Ki-moon," Iran's Deputy Foreign Minister for European and American Affairs Majid Takht-e-Ravanchi said Sunday.

"Hamid Aboutalebi has been nominated as the ambassador of Iran to the UN and this issue is not related to Iran-US ties for which the US would refuse to issue a visa for an Iranian citizen," Takht-e-Ravanchi added.

The US refused to issue a visa to Hamid Aboutalebi April 11 for being involved in the siege of the US embassy in Tehran in 1979.

The refusal of the visa has prevented Aboutalebi from taking up his position at the UN headquarters in New York.

The US House of Representatives and the Senate have both voted in favour of a bill barring Aboutalebi from entering the US.

The bill still requires US President Barack Obama's signature for it to become law.

Iran has rejected the decision saying that Aboutalebi is one of its most experienced diplomats and so it stands by his nomination.

Aboutalebi has denied being a part of the group that took over the US embassy in Tehran in 1979.

Fifty-two US diplomats and citizens were held hostage for 444 days (Nov 4, 1979 to Jan 20, 1981) by pro-Iranian Revolution students.

The hostage crisis came as a blow to the US, which had supported the overthrow of the then Iranian ruler, Mohammad Reza Pahlavi.