Asked about news accounts that Iran had taken a new step in uranium enrichment, Bush replied: "It says to me that we must double our effort to work with the international community to persuade the Iranians that there is only isolation from the world if they continue working forward on such a program."
His comments came after the Iranian news agency ISNA reported on Friday that Iranian scientists had begun feeding gas into a second cascade of centrifuges to enrich uranium, defying United Nations threats of sanctions over Iran's nuclear program.
"I've read the speculation about that that's what they may be doing," Bush told reporters after a meeting at the White House with NATO Secretary General Jaap de Hoop Scheffer.
"But whether they double it or not, the idea of Iran having a nuclear weapon is unacceptable. It's unacceptable to the United States, and it's unacceptable to nations we are working with in the United Nations to send a common message" to Tehran, said Bush.
Tehran's announcement came as six major powers huddled behind closed doors in New York to review a draft UN Security Council resolution mandating sanctions against Iran over its refusal to halt its sensitive nuclear fuel work.
Iran denies it has a nuclear weapons program, maintaining that the project is aimed solely at producing electricity.
State Department spokesman Sean McCormack said Washington was awaiting an International Atomic Energy Agency report to confirm whether the centrifuges were indeed being fed.
"We're obviously not on the ground there; the IAEA is there," McCormack told reporters.
"The IAEA has its own procedures," he acknowledged. "But usually, if there is a sudden development, and an important development such as this, I imagine the IAEA headquarters would be notified relatively quickly."
Still, he remained cautious about the efforts announced by Tehran.
"The inspectors have to satisfy themselves that they understand exactly what it is that they're seeing and be able to confirm that with scientific testing or empirical evidence," McCormack said.
Copyright AFP (Agence France-Presse), 2006
