Obama signs law barring Iran U.N. envoy

President Barack Obama on Friday signed into law a bill barring entrance to the U.S. for any foreign diplomat seen as a threat to American security or who has engaged in "terrorist activity" — a measure that effectively bans Iran’s ambassador to the United Nations.

Washington said earlier this week that it would not issue a visa to Iran's pick for U.N. envoy, Hamid Aboutalebi, because he is suspected of involvement in the 1979 hostage crisis at the U.S. Embassy in Tehran.

"Acts of espionage and terrorism against the United States and our allies are unquestionably problems of the utmost gravity," Obama said in signing the measure, an amendment to current U.S. legislation. "I share the Congress' concern that individuals who have engaged in such activity may use the cover of diplomacy to gain access to our nation."

The new law, S.2195, bars the entrance onto U.S. soil of "any representative to the United Nations who the president determines has been engaged in terrorist activity against the United States or its allies and may pose a threat to United States national security interests." Obama, however, added in a statement that the measure should be taken as an "advisory," because it could potentially interfere with his "constitutional discretion" to receive or reject ambassadors.

Starting in November 1979, dozens of American diplomats and staff were held for 444 days by radical Iranian students at the U.S. Embassy in Tehran following the overthrow of the pro-Western shah. The protracted standoff profoundly shocked the United States and led to the severing of all diplomatic ties between the U.S. and Iran for the past three decades.

Aboutalebi, a veteran diplomat who currently heads Iranian President Hassan Rouhani's political affairs bureau, said he served a limited role as a translator for the students who took the Americans hostage, but denied he was part of the actual hostage taking.

The spat over Aboutalebi's nomination comes amid a cautious thaw in relations between the U.S. and Iran, as Tehran's new leadership seeks to negotiate a nuclear treaty with global powers.

Iran, for its part, has refused to name an alternate choice for the ambassadorship. "We have no replacement for Mr. Aboutalebi and we will pursue the matter via legal mechanisms envisioned at the United Nations," said Abbas Araghchi, a senior Iranian Foreign Ministry official, according to IRNA news agency.

"Based on an agreement with the United Nations, America is bound to act according to its international commitments," Araghchi said.

Indeed, as the host government for the U.N., the United States is generally obliged to issue visas to all diplomats who are chosen by member nations as representatives.

The United Nations said it had no comment at this time on the U.S. decision.

Al Jazeera and wire services