While maintaining that their country is not developing nuclear weapons, Iranians argue strenuously and with rare unanimity that they have a right to such weapons, to balance Israel's arsenal and as a manifestation of national pride.

Iran's defense of its right to obtain nuclear arms cuts across the country's deep political divide, recent interviews here showed, uniting the conservative clerics who occupy powerful appointive offices and the elected reformers who challenge the conservatives on most topics. Leading theoreticians at opposite poles find common ground articulating a national ambition that diplomats warn could hold the seeds of a crisis if it is realized.

"Are nuclear weapons bad?" asked Amir Mohebian, an unofficial adviser to Iran's supreme leader, the conservative Ayatollah Ali Khamenei. "Why don't you make the same protest against Israel?"

"It's basically a matter of equilibrium," said Mostafa Tajzadeh, a leading theorist in the reform movement that controls Iran's parliament. "On the one hand Israel says, 'If I don't have it, I don't have security.' And we say, 'As long as Israel has it, we don't have security.'

"We believe the way to deal with Israel's expansionism is to democratize the region," Tajzadeh said. "But while things are the way they are, public opinion in Muslim countries, and in Iran, is not going to be against having nuclear weapons."

U.S. officials have expressed surprise and alarm at the rate Iran has been developing its nuclear capabilities, after they were briefed by inspectors from the International Atomic Energy Agency following inspections last month. The U.N. inspectors toured new nuclear facilities that Iran had revealed "only when asked about them," said a foreign diplomat in the Iranian capital. "If they had peaceful intentions, there's no reason why they shouldn't declare them from the start."

The inspections determined that a new complex in the central desert town of Natanz could be producing enriched uranium in three years, and experts say the material could be diverted to make nuclear bombs. Independent experts said satellite photos show a facility under construction near the town of Arak that appears to be a heavy water reactor. Another reactor at Bushehr, on the Persian Gulf, being built with Russian help and fuel, is scheduled to go on line this year, Iranian officials have said.

Iran maintains that its ambitious nuclear program is geared only toward energy. As a signatory to the nuclear Non-Proliferation Treaty, officials note, Iran can rely on nuclear power to supply 20 percent of its energy needs under IAEA guidelines, despite its vast natural gas and petroleum reserves.

"We do need nuclear energy," said Mohebian, an editor at the conservative newspaper Resalat. "Because of an incorrect distribution of people around the country, we do have certain problems."

But during interviews, he and others moved quickly to other explanations. "The Americans say, in order to preserve the peace for my children, I should have nuclear weapons and you shouldn't have them," Mohebian said.

"It's a double standard," said Shirzad Bozorgnehr, the reformist editor of Iran News, an English-language daily. "If a signatory of the non-proliferation treaty is subscribing to the so-called community of civilized nations, then why has Israel not been sanctioned?

"I hope we get our atomic weapons," Bozorgnehr said. "If Israel has it, we should have it. If India and Pakistan do, we should, too."

Hostility toward Israel, which is widely understood to have nuclear weapons, is a touchstone of Iranian politics. It is also an impediment to restoring diplomatic relations with the United States, severed after the 1979 takeover of the U.S. Embassy in Tehran.

The United States has put Iran on its list of nations that support or sponsor terrorism. But U.S. officials say it was pursuit of weapons of mass destruction that assured Iran a place on President Bush's "axis of evil," along with Iraq and North Korea. The designation infuriated and dismayed Iran's political establishment, coming just weeks after the two governments had cooperated in the campaign against the Taliban in Afghanistan.

"It's interesting to see Iranian reactions," said the foreign diplomat. "I think it's just sinking in now that 'axis of evil' was as much about weapons of mass destruction as about terrorism."

To Iranians, however, joining the nuclear club is also about pride. The country known through most of its 2,500-year history as Persia has the self-regard of an empire.

"Iran is a unique country," said Sayed Asadullah Maryan, an adviser to the Defense Ministry. "No country in the region has our history and culture and civilization. If the Americans understood us, they would know, as with India and Pakistan, how difficult it is to live under the nuclear shadow of Russia and the nuclear shadow of Israel."