The White House says there is growing international support for action by the U.N. Security Council on Iran's nuclear program. The Bush administration says Tehran is showing it cannot be trusted to abide by its international obligations.
Iran says it is resuming nuclear fuel research. The Bush administration warns it could face serious consequences.
White House spokesman Scott McClellan says the issue is a matter of trust.
"Iran has shown over the course of the last couple of decades that it cannot be trusted," he said. "They have concealed their activities from the international community. They have violated their agreements with the international community. It is time for Iran to come into compliance, to abide by the agreements they have made and to meet the demands of the international community."
Iran says its nuclear program is for civilian use only, but the United States says Tehran is trying to get the technology needed for nuclear weapons.
France, Britain and Germany have been leading negotiations with Iran regarding its nuclear program, and McClellan says the United States continues to support their efforts. But at the same time, he makes clear that U.S. patience is running out.
McClellan says a growing majority on the Board of Directors of the International Atomic Energy Agency has called on Iran to act in good faith and move forward in negotiations with the so-called "European Three." The White House spokesman says if there are no results, the next step may well be a U.N. referral and the possibility of sanctions.
"Then the option before us would be referral to the Security Council and there is a growing majority in the international community that is looking at that," he added.
But Russia and China have indicated they are reluctant to take Iran before the Security Council, where they have permanent seats and veto power. During a briefing for reporters, McClellan said only that discussions with Beijing and Moscow are ongoing.
"We will continue to discuss with all our friends and allies and partners how to move forward to address this issue. This is a serious matter. It is a serious concern," he explained.
At the State Department, spokesman Sean McCormack said one option under consideration is calling an emergency meeting of the IAEA. A senior state department official claimed a high degree of coordination on the matter among the five permanent Security Council members. This official -- who spoke on the condition he would not be identified -- said Russia, China, Britain, France, and the United States are delivering very similar messages to Iran urging Tehran to drop its threat to resume nuclear research and return to negotiations.