TEHRAN, Iran – Iran yesterday blamed American sanctions and European restrictions for denying Tehran access to advanced civilian nuclear technology, forcing it to keep the program secret in its early days and driving the country to the black market for needed materials.

Despite the initial secrecy, Iran now openly admits that it has already achieved proficiency in the full range of activities involved in enriching uranium – a technology that can be used to produce fuel for nuclear reactors or atomic bombs.

Washington has accused Tehran of using its civilian nuclear program as a cover to build a nuclear bomb. Iran denies the charge, claiming its nuclear program is designed to generate electricity.

“True. There was secrecy,” said Hashemi Rafsanjani, the former president. “But secrecy was necessary to buy equipment for a peaceful nuclear program.”

“If sanctions had not been imposed on us, we would have declared everything publicly, but we had problems buying metal. Nobody sold us anything in the market,” he said.

Mr. Rafsanjani was speaking at the closing session of a two-day international conference on nuclear technology in Tehran, attended by more than 50 international nuclear scientists.

President from 1989-97, Mr. Rafsanjani is also chairman of the Expediency Council, a powerful body that arbitrates between the Parliament and another council that approves proposed legislation. He is believed to have a great influence over Iran’s nuclear program.

Since last year, Iran has publicly acknowledged that it once bought nuclear equipment from middlemen in south Asia, lending credence to reports that the father of Pakistan’s nuclear bomb, Abdul Qadeer Khan, was one of the suppliers.

Mr. Rafsanjani said Iran resorted to the black market because of political “injustice” by America and Europe.

He said Washington and the Europeans had approved the building of 20 nuclear power plants in Iran and provide advanced nuclear technology when Tehran was under the pro-Western shah in the 1970s. But they reversed course after the 1979 Islamic revolution that toppled the shah and brought the late Ayatollah Ruhollah Khomeini to power.

“If the Shah is in Iran, you would give him nuclear technology, but if Imam [Khomeini] is in Iran, you can’t do that … the history of nuclear energy in Iran is a lesson in contradictions in Western policy toward Iran,” he said.

But Mr. Rafsanjani said Iran has been very transparent since 2002, when aspects of its nuclear activities were revealed. He said the country had cooperated with the International Atomic Energy Agency, the U.N. nuclear watchdog, to dispel suspicions that it was seeking nuclear weapons.

He said Iran would never agree to a permanent halt on enriching uranium, a technology he says Tehran is entitled to under the Nuclear Nonproliferation Treaty.

Iran suspended its uranium-enrichment activities last year to create confidence and avoid U.N. Security Council sanctions. But Tehran says maintaining the voluntary freeze depends on progress in ongoing talks with Britain, Germany, and France, who are negotiating on behalf of the European Union.

“Definitely we can’t stop our nuclear program and won’t stop it. You can’t take technology away from a country already possessing it,” Mr. Rafsanjani said.