Image copyright Getty Images Image caption Aboutalebi denies he was part of the core group that took the US diplomats hostage in 1979

The US Congress has sent a bill to the president that would bar Iran's pick for ambassador to the UN from entering the country.

The House of Representatives passed the measure unanimously two days after the Senate approved it.

Hamid Aboutalebi was a part of the Muslim student group that seized the US embassy in Tehran in 1979.

The White House has told Iran Mr Aboutalebi was "not viable" but has not taken a position on the bill.

Fifty-two Americans were held for 444 days at the height of Iran's Islamic revolution, which saw pro-American Shah Mohammad Reza Pahlavi sent into exile and Ayatollah Ruhollah Khomeini take power.

Mr Aboutalebi, who previously served as Iran's ambassador to Belgium, the European Union, Italy and Australia, told Iranian media his participation in the hostage crisis began only after the initial seizure of the embassy, and primarily involved translation.

'Unequivocal message'

On Thursday, White House spokesman Jay Carney said, "We've made clear and have communicated to the Iranians that the selection they've put forward is not viable."

But he declined to say whether President Barack Obama would sign the bill into law.

The Iranian government, meanwhile, has called the US rejection of Mr Aboutalebi "not acceptable".

The bill passed on Thursday in the House denies entry into the US to individuals engaged in espionage or terrorism or who pose a threat to national security.

Senator Ted Cruz, the Texas Republican who introduced the legislation in the US Senate, urged Mr Obama to sign the bill.

"We, as a country, can send an unequivocal message to rogue nations like Iran that the United States will not tolerate this kind of provocative and hostile behaviour," Mr Cruz said.

The bill's sponsor in the House, Republican Doug Lamborn, said, "Terrorists, from Iran or elsewhere, should not be allowed to walk the streets of Manhattan with diplomatic immunity."

US options

As the host country of the United Nations, the US has previously but rarely denied entry to an envoy or head of state. Those included a previous Iranian diplomat and Sudanese President Omar al-Bashir.

In those cases the applications were withdrawn after the US signalled opposition, or the state department simply declined to process the visas.

Those options are available in Mr Aboutalebi's case.

On Monday, Iranian foreign ministry spokeswoman Marzieh Afkham told state-run media he had previously received a US visa as part of a visit to the UN in the 1990s.

In an interview with an Iranian news site, Mr Aboutalebi said he was not part of the group that took over the US embassy and was only later asked to translate for the students.

Others involved in the hostage-taking have corroborated that account.