President George W Bush says the stand-off with Iran presents a "grave national security concern" for the US.
Iran has vowed to stand firm in the face of Western pressure
Mr Bush based this on the Iranian leader's threat to destroy Israel, and Washington's belief that Tehran is seeking to develop nuclear weapons.
It is essential to resolve these issues diplomatically and "to deal with these threats today", Mr Bush said.
The five permanent UN Security Council members are meeting on Friday to discuss Iran's nuclear programme.
Ambassadors from US, UK, France, Russia and China are to work in private on a statement to put before the full council next week.
Meanwhile, EU foreign policy chief Javier Solana has said that the war of words between Iran and US is "not in line with normal diplomacy".
Mr Solana lamented the escalation, including an Iranian threat to cause "harm and pain".
"These kind of remarks... are always very inflammatory. They are not in line with normal diplomacy. My concern is not such comments, but what reactions they could produce," he said.
Mr Solana also said he did not rule out the possibility of sanctions against Iran. But he added that there was still time for diplomacy and said Europe didn't want to target the Iranian people.
On Wednesday, the United Nations nuclear watchdog the IAEA decided to report Iran to the Security Council.
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.
The IAEA report, which was widely leaked to the media last week, said that the Iranians had begun feeding uranium gas into centrifuges, a first step in a process that can produce fuel for nuclear reactors or bomb material.
America's UN ambassador, John Bolton, told the BBC the issue would strongly test the council.
He said 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.
Iran's Supreme Leader, Ayatollah Ali Khamenei, has said his country will "stand like steel" against any pressure.