All five permanent members of the U.N. Security Council have each separately sent to Iran a diplomatic communiqué — known as a 'demarche' in international parlance — warning the Islamic Republic that it could face sanctions should it go forward with its nuclear program.
Bush administration officials told FOX News that the communiqués, sent Saturday, are an important step forward in blocking Iran's nuclear ambitions because China and Russia, which have huge economic interests in Iran, have hinted in the past that they would oppose and veto such a referral if brought to the Security Council.
"We are working very closely with Russia, China and France and Britain on sending a clear message to the Iranians," State Department spokesman Sean McCormack said.
The five permanent members of the U.N. Security Council are the United States, United Kingdom, France, Russia and China. Each has veto authority on the 15-member panel that enables them to thwart resolutions.
On Sunday, Iran announced it would resume its nuclear program, which it says is being used only to develop peaceful civilian energy. The United Nations, United States and European Union all suspect Iran of using the energy program to secretly build nuclear weapons.
Hossein Ghafourian, head of the nuclear research center of Iran's atomic energy organization, pledged to press on with plans to continue its peaceful program.
"Blocking research activities is similar to blocking the light," Ghafourian told state-run radio on Sunday.
White House spokesman Scott McClellan strongly criticized Iran on Monday.
"This is a matter of trust when it comes to Iran, and Iran has shown over the course of the last couple of decades that they cannot be trusted. They have concealed their activities from the international community. They have violated their agreements with the international community. It's time for Iran to come into compliance, to abide by the agreements they made, and to meet the demands of the international community. The international community has spelled out what those demands are," McCellan said.
Sources say the five permanent members sent separate communiqués because China and Russia repeatedly tried to soften the language of the warning and no consensus could be reached for a joint warning.
While pleased that China and Russia delivered separate warnings to Iran, Bush administration officials say they are very cautious about prematurely assuming that China and Russia are willing to get tough with Iran and support sanctions.
"Ultimately, given Iran's track record on seeking nuclear weapons under the cover of a civilian program, defying the international community, bobbing and weaving, obfuscating, that we're ultimately all going to end up in the Security Council on this issue," said McCormack.
But one senior administration official suggested that both China and Russia sent their demarches reluctantly and might in the end oppose a referral and or sanctions. Nonetheless, McCormack said the efforts by China and Russia are noteworthy.
"I think that the Chinese are perfectly capable of delivering their own messages," McCormack said. "What we have been doing, have done and will continue to do, is to continue to work with them, work with the Russians and others so that Iran receives a clear, consistent, unmistakable message from the rest of the world."
One senior official told FOX News that the demarches from each of the five permanent Security Council members urged Iran to resume talks with the EU-3, comprised of Germany, France and the U.K.
The United States is backing a stalled European effort to negotiate with Iran, and supports a separate offer from Russia to perform some of the most sensitive nuclear enrichment tasks on Iran's behalf. Both initiatives would allow Iran to pursue legitimate civilian nuclear energy while reducing the risk that the same technology could be diverted to make weapons.
Negotiations aimed at getting Iran to give up its nuclear aspirations by the EU-3 have been stalled for months as Iran has insisted it has a right to nuclear energy and does not seek weapons. The EU-3 have all issued strong rebukes against Iran for its announcement that it would resume its nuclear research and development.
French Foreign Minister Philippe Douste-Blazy called on Iran on Monday to immediately retract its decision to restart nuclear activities. He said the EU-3 would meet on the issue soon.
Douste-Blazy also called Iran's intention to restart nuclear activities linked to uranium enrichment "reason for very serious concern."
"We call on Iran to go back on its decision without delay and without conditions," Douste-Blazy said.
German Foreign Minister Frank-Walter Steinmeier said earlier Monday that Iran was sending "very, very disastrous signals" on its nuclear program that "cannot remain without consequences for the EU-3's negotiation process."
Javier Solana, the European Union foreign and security affairs chief, told Iran on Saturday that if it resumes its uranium enrichment program, it may doom any further negotiations with the 25-nation bloc about economic aid and other issues.
During President Bush's trips to Europe last year he sought, and aides say received, assurances from the EU-3 that if talks failed, they would support a U.N. Security Council referral for sanctions.
The U.N.'s top nuclear watchdog at the International Atomic Energy Agency told Sky News last week that he is losing his patience with Iran. Mohammed El Baradei makes his next report in March and administration officials say by that time it will be clear if Russia and China will support sanctions.
FOX News' Carl Cameron and The Associated Press contributed to this report.