The United States said on Tuesday that it has told the Iranian government about its "not viable" selection of a new United Nations ambassador for his alleged involvement in holding 52 Americans hostage in 1979.

"The US government has informed the government of Iran that this potential selection is not viable," White House spokesman Jay Carney said at a regular news briefing.

The US Senate on Monday passed a legislation denying entry of Hamid Aboutalebi, Iran's proposed new UN ambassador, on the grounds that he was a member of a militant group that seized the U. S. embassy in Tehran on Nov. 4, 1979 and held 52 Americans hostage for 444 days.

A similar measure is pending in the House of Representatives. If passed by both chambers, the bill will be sent to President Barack Obama for his signature into law.

"We share the Senate's concerns regarding this case and find the nomination is extremely troubling," Carney said.

Iran on Tuesday defended Aboutalebi, a 56-year-old veteran diplomat who had served as the country's ambassador to Australia, the European Union, Belgium and Italy.

Foreign Ministry spokeswoman Marzieh Afkham called Aboutalebi a qualified diplomat for the UN post, but said Tehran was pursuing the issue through diplomatic channels and would make proper decisions after receiving response from official sources.