The United States said Friday it would not grant a visa to Iran's newly appointed UN ambassador, who has been linked to the 1979 hostage crisis, threatening to cloud a gradual thaw in relations.
Tehran says Washington's objection to Hamid Aboutalebi is unacceptable and the situation appears to be heading towards stalemate, as well as posing a challenge to President Barack Obama's drive for a diplomatic breakthrough after decades of mistrust between the two sides.
As the host government of the United Nations, the US is obliged to issue visas to diplomats who serve at the New York-based world body and it is believed that Washington has never denied a visa for a UN ambassador, although Tehran withdrew its nominee once in the early 1990s.
Fierce political pressure from Congress, which has overwhelmingly passed a bill barring Aboutalebi from US soil and where skepticism of Obama's nuclear diplomacy runs high, has put the White House in a corner.
"We have informed the United Nations and Iran that we will not issue a visa for Mr Aboutalebi," White House spokesman Jay Carney said.
Carney said White House lawyers were studying constitutional issues raised by the bill which landed on Obama's desk on Thursday, and did not say whether he would eventually sign it.
But he added: "We certainly share the intent of the bill passed by Congress."
Carney said that there was no reason to expect that the row between Tehran and Washington over the envoy would impact progress in talks between Iran and world powers, including the United States, over Tehran's nuclear program.
- ' Not viable' -
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The episode reflects the impact the hostage crisis -- in which 52 Americans were held for 444 days in Tehran -- still has on US perceptions of the Islamic Republic.
Neither Carney nor the State Department directly put down the decision not to give Aboutalebi a visa down to suspicions over his role in 1979, but noted widespread media reports on his background.
Iran had slammed as unacceptable a previous US statement that the nomination of Aboutalebi was "not viable."
Despite the impasse, a senior State Department official did note that Iran still has time to withdraw the nomination.
Whether that would be a politically palatable option for President Hassan Rouhani's government remains unclear, however.
Aboutalebi, a veteran diplomat who currently heads Rouhani's political affairs bureau, has insisted he was not part of the hostage-taking in November 1979, when a Muslim student group seized the US embassy after the overthrow of the pro-Western shah.
He has acknowledged he served a limited role as a translator for the students who took the Americans hostage.
But US lawmakers who passed the bill branded Aboutalebi a "terrorist" and say he should not be allowed to walk around the streets of New York with diplomatic immunity.
Democratic Senator Chuck Schumer praised the White House for its stance on the ambassador.
"Hamid Aboutalebi's nomination would have been a slap at all American victims of terrorism, not just those taken hostage in 1979," Schumer said.
"We're glad the Obama administration made this choice, and Iran should stop playing these games."
The bill amends a section of the existing Foreign Relations Authorizations Act to allow Washington to withhold visas for individuals who have "engaged in a terrorist activity against the United States."
UN spokesman Stephane Dujarric said Aboutalebi's fate was a matter between Tehran and Washington and said the world body had not been consulted by either side.