Influential cleric and former President Akbar Hashemi Rafsanjani warned at Friday prayers today that the United States must stop what he called threatening his country or Iran would step up its nuclear program.
Secretary of State Condoleezza Rice has advised Iran's leaders to stop developing what she deemed a nuclear weapons program. Rice has emphasized diplomacy but the United States has not ruled out a potential attack.
Rafsanjani also suggested that if France, Britain and Germany do not make trade concessions soon, "We will, God willing, continue with our enrichment and nuclear technology."
"The Persian Gulf is not a region where they can have fireworks, and Iran is not a country where they can come for an adventure," he added.
Iranian officials say the technology is strictly for peaceful nuclear power, but U.S. officials believe Iran is developing a nuclear weapon.
Inspectors from the United Nations' International Atomic Energy Agency, who arrived back in Iran today, have found no evidence of a nuclear weapons program here. But they have confirmed that Iran secretly acquired materials for an energy program that could be eventually used to make a bomb.
"What we do know is that, yes, for almost 20 years they did conceal all of this activity, and it was a wide range of activity," said IAEA spokesman Mark Gwozdecky.
At the prayers, Iran's leaders used U.S. opposition to its nuclear program to stir anti-American feelings.
Virtually every public event in Iran now includes some reference to President Bush and nuclear weapons. It has become, at least politically, the most talked-about subject in the country.
Many of the Iranians who spoke to ABC News today were divided on the question of nuclear weapons.
"Yes, I think it's necessary for every country in the world [to have weapons] for their security. [It's] OK because others have them," said one man.
"With this regime that we have, it's better that they don't have such weapons," one student said in Farsi, speaking through an ABC News translator. "Why should we have nuclear weapons? For what purpose?" asked another.
Some Iranians told ABC News they are concerned the United States might use force to destroy their nuclear program. But Iran's current president, Mohammed Khatami, told a crowd of thousands this week, if anyone attacks, "Iran will turn into a scorching hell for the aggressors."
ABC News' Bob Woodruff filed this report for "World News Tonight."