The latest diplomatic drive follows a report by the United Nations nuclear watchdog which concluded Iran had done little to answer questions about its nuclear program.
Iran maintains that its nuclear program is for peaceful purposes to generate power.
But the UN wants a halt to its sensitive research amid Western fears that Tehran plans to develop nuclear weapons.
Diplomatic push begins: Bush
President Bush said diplomatic efforts are “just beginning,” adding that the UN report should be a reminder that the Iranian government’s intransigence is not acceptable.
"Iran's desire to have a nuclear weapon is dangerous, in my judgment, and the diplomatic process is just starting," US President George W. Bush said.
The US ambassador to the United Nations, John Bolton, said he would press for the quick adoption of a resolution that would legally bind Iran to freeze its uranium enrichment.
The United States has called for a UN Security Council resolution against Iran under Chapter 7 of the UN Charter, which could impose economic sanctions and open the way for possible military action.
Russia and China have spoken against imposing UN sanctions on Iran and Bush highlighted the need for a "common voice" to put pressure on Tehran.
"The world wasn't always of like mind that the Iranians were headed for a weapon and that that would be a dangerous course of action," Bush said.
"And now we are of like mind. And so we are in the stage now of formulating a strategy to achieve a diplomatic solution to this problem."
Allies want strong response
US allies called for a strong response at the United Nations.
British Foreign Secretary Jack Straw said it was "very serious that the Iranian regime has failed fully to co-operate with the IAEA and the United Nations Security Council."
"We will now be asking the Security Council to increase the pressure on Iran, so that the international community can be assured that its nuclear programme is not a threat to peace and security," he added.
British Prime Minister Tony Blair's office called the IAEA report worrying and reaffirmed the need for common agreement on the next diplomatic measures.
France, which along with Britain and Germany held unsuccessful talks with Iran, expressed deep concern over Iran's failure to comply with international demands but said negotiations were still possible.
"It's an alarming situation for the entire international community," said French Foreign Minister Philippe Douste-Blazy. "We continue to say to Iran however that the door to negotiations has not been closed."
After attending a NATO meeting, German Foreign Minister Frank-Walter Steinmeier said foreign ministers of the 26-nation transatlantic alliance agreed that the international community should form a strong united front.
"We agreed that in further discussions at the Security Council, the international community should now stand firm so as to make clear to Iran what the negative consequences of self isolation would be," he said.
US faces opposition
The Western push for a tough stance against Iran at the UN faces opposition from Russia and China, two of the five permanent, veto-wielding members of the UN Security Council. The other permanent members are the United States, Britain and France.
China's UN envoy, Wang Guangya, restated Beijing's opposition to Western plans to invoke Chapter 7.
"I believe that invoking Chapter 7 will (make things) more complicated, and the implications will lead events to a direction that is uncertain," Wang said.
"We all know what Chapter 7 is... Clearly this would not be the end of the resolutions, this would be the beginning of a series of resolutions. Whatever we do we should promote diplomacy," he added.
A Chapter 7 resolution is invoked to deal with "threats to peace, breaches of the peace, or acts of aggression" and is binding on all UN member states. It can authorize sanctions or even military action.
The five foreign ministers of the Security Council's five permanent members plus Germany will meet on May 9 to discuss the crisis, the US State Department said.
Iran, which rejects allegations that its civilian nuclear program is a cover for developing a bomb, insisted that the IAEA report contained "no negative points" and argued the issue should not be taken up by the Security Council.
Mohammad Saidi, the deputy head of Iran's Atomic Energy Organisation, said it would be a "bad way" to go to the Security Council.