The International Atomic Energy Agency, in its latest report, expressed concern about upgraded centrifuges at the Natanz enrichment facility in Iran. IAEA inspectors have been unable to access the Parchin military complex outside Tehran, prompting the U.N. nuclear watchdog to say it can't verify the intent of Iran's nuclear program.
Rice said, following a closed-door U.N. Security Council briefing, that the IAEA report showed there were growing risks associated with Iran's nuclear ambitions.
"The Iranian nuclear issue remains one of the gravest threats to international security and a top priority for the Security Council," she said.
A second round of meetings between the five permanent members of the Security Council, Germany and Iran is scheduled for April in Kazakhstan. Rice said Washington remains committed to dialogue as well as economic pressure.
"Working together, we can continue to clarify for Iran the consequences of its actions and show Iran the benefits of choosing cooperation over provocation," she said.
Iranian envoy to the IAEA Ali Asghar Soltanieh was quoted by Iran's Press TV as saying Tehran viewed the allegations made in the latest report as "baseless."