Washington has warned that Iran's nuclear programme is one of America's biggest challenges, and refused to rule out any option including military.
Iran has begun the process to produce its own nuclear fuel
Senior officials were speaking a day after United Nations nuclear watchdog the IAEA decided to report Iran to the Security Council.
America's UN envoy told the BBC the issue would strongly test the council.
Secretary of State Condoleezza Rice said earlier that Iran might present the US with its toughest challenge.
Iran has vowed to resist international pressure, insisting it has the right to civilian nuclear technology. It denies US and EU accusations that it is seeking to develop nuclear weapons.
UK Foreign Secretary Jack Straw said the world supported Iran's right to nuclear energy but it must make fully clear its intentions.
"Until they clarify their intentions, we don't believe that it is safe for them to have full access to the nuclear cycle," he told the UK's Channel 4 television.
The five permanent members of the UN Security Council are due to meet to discuss the issue later on Friday behind closed doors.
They hope to work out a statement to be adopted by a full meeting of the council next week.
Washington is clearly delighted that the Security Council will finally discuss Iran's nuclear activities, the BBC's Susannah Price reports from the UN.
But it is far from clear what concrete action members will be able to agree on, with China and Russia likely to oppose moves such as sanctions.
US Ambassador John Bolton told the BBC he could not predict whether there would be any consensus at the Security Council which faced, he said, a test as to its ability to deal with the threat of nuclear proliferation.
"The president [George W Bush] has said repeatedly that no options are off the table," he said.
But Washington's preference was to deal with Iran through the Security Council, he added.
Mr Bolton said that while much of what Iran did was bluff, its level of irresponsibility illustrated why Tehran should not be allowed to develop nuclear weapons.
Ms Rice told a Congressional hearing in Washington that Iran seemed determined "to develop a nuclear weapon in defiance of the international community".
She described the country as the "central banker for terrorism" in the Middle East, and a block to democracy.
"We may face no greater challenge from a single country than from Iran," she said.
The report forwarded to the UN Security Council was written by the International Atomic Energy Agency (IAEA).
Iran has been holding rallies to defend its nuclear programme
Leaked to the media last week, it says the Iranians have begun feeding uranium gas into centrifuges, a first step in a process that can produce fuel for nuclear reactors or bomb material.
Russian Foreign Minister Sergey Lavrov, whose country is Iran's main nuclear technology supplier, appealed on Thursday for the IAEA to be allowed to remain the main arbiter in the dispute.
"They have a thorough knowledge of all the technical details of Iran's nuclear programme and without those technical details it's extremely difficult to take the right decisions," he said in New York.
He added that the Iranians were "doing nothing to enable the problem to be examined calmly and professionally".
Iran's Supreme Leader, Ayatollah Ali Khamenei, has said his country will "stand like steel" against any pressure.