The resolution mainly affects military purchases and financial transactions of the Islamic Revolutionary Guards Corps.

As a result of this resolution, "E. T. S. is currently unable to process payments from Iran."

The statement posted on the E. T. S. Website on Wednesday cited the United Nations Security Council resolution "affecting banks and financial institutions that conduct business in Iran."

Experts and Iranian expatriates were appalled, saying that if the sanctions prohibited Iranians from studying abroad, they would hurt precisely the kind of outward-looking young Iranians the West would like to help.

The Educational Testing Service has announced that it is temporarily suspending registration for its tests in Iran, including the popular TOFEL test.

President Obama signed into law additional unilateral sanctions, including restrictions on foreign banks that do business with the Revolutionary Guards or other blacklisted Iranian institutions.

The United Nations Security Council approved a fourth round of sanctions against Iran in June.

Karim Sadjadpour, an Iran expert at the Carnegie Endowment for International Peace, said:

"Our intent remains to apply pressure on the Iranian government without placing an undue burden on the Iranian people," he said.

A State Department spokesman, Philip J. Crowley, said the government was "exploring whether there are alternative mechanisms" to allow E. T. S. to continue its work in Iran.

"Prohibiting TOEFL from operating in Iran is counterproductive to the spirit of smart sanctions. The government is not being hurt by TOEFL not operating in Iran, it's the people, and precisely the people we're hoping to empower."