WASHINGTON - The Taliban government of Afghanistan is history and so is the Baathist regime of Saddam Hussein. Could the mullahs of Iran be next?

A growing number of neoconservatives, both in the administration of President George W. Bush and out, say the answer is yes.

Many of them contend that Iran's Islamic government is ripe for the picking, with widespread public disillusionment, an anemic economy and mounting opposition. Others say the United States can't afford to wait, given Iran's strong ties to terrorist groups and its apparent drive for nuclear weapons.

"We'll never have true stability in the region as long as the Iranian regime remains in power," says Sen. Sam Brownback, R-Kan., a leader among neoconservatives in Congress. "We can never establish a free and secure Iraq or Afghanistan as long as the Tehran regime remains intact."

With nearly 70 million people, Iran is home to over 10 percent of the world's known oil and gas reserves. It is the world's longest-lasting Islamic republic and a place of surprisingly lively public discourse, with keen memories of past U.S. interventions and little stomach, many believe, for repeating the violent upheaval that characterized the 1979 revolution.

"Iran is not Iraq," says Gary Sick, a specialist on Iran and director of the Middle East Institute at Columbia University. "It's not North Korea and it's not even Syria. It is a government which has some really odious aspects but it is not, strictly speaking, a dictatorship."

The neoconservatives insist they will, with U.S. help - and that if they don't the United States will pay the price, in Iraq and Afghanistan and across the world.

"We're riding a horse and we're in the middle of the stream," Brownback told a conference last week at the American Enterprise Institute. "We've got to press on to the other side."

Brownback insisted that Iran's government was most vulnerable at home, so much so that merely publicizing U.S. support would bring rebellion into the streets. He is pressing for congressional action on legislation that would make regime change in Tehran official U.S. policy and give exiled Iranians federal help for television and radio broadcasts home.

Critics counter that Bush issued that kind of statement last July, assailing Iran's government and supporting dissidents, but it caused scarcely a ripple on the streets of Tehran.

Former CIA analyst Reuel Gerecht warned that as Iran approaches nuclear-weapons capability the United States may be forced to take military action.

Iran acknowledged in February what opposition groups had already leaked: that it was building a uranium-enrichment plant near the central Iranian city of Natanz. Such facilities are permitted under the Non-Proliferation Treaty of 1970, but they would also give Iran the capability of producing weapons-grade uranium at factory rates.

Mohammed elBaradei, the director of the International Atomic Energy Agency, inspected Iran's fuel-cycle facilities in March as well as the light-water reactors near the Persian Gulf city of Bushehr that Iran has rebuilt with Russian help. Those reactors are scheduled to go on line as early as June, giving Iran a source of spent fuel that might then be reprocessed into weapons-grade plutonium.

The administration is pressing the agency to produce a full report on Iran's nuclear activities by mid June. An agency finding of non-compliance would put the matter before the U.N. Security Council, where U.S. officials could find themselves debating the role and powers of U.N. weapons inspectors yet again.

Or resorting, yet again, to a preemptive military strike - should Iran's nuclear program cross a "red line" that no one in the administration has yet defined.

At that point "we'll have only two options - either to punt, or to go after the facilities," Gerecht said. "I'm inclined to go after the facilities, although it's not an easy task, by any means, and we would have to be prepared for potential bloodshed in doing so."

The lead example of such preemptive action, long cited by neoconservatives, was the Israeli air force's bombing of Iraq's Osirak nuclear power plant in 1981. President Ronald Reagan condemned the attack at the time, but analysts in Israel and elsewhere contend it achieved a significant slowdown in Iraq's nuclear power program.

Other experts have reached a different view, among them David Albright, a former United Nations weapons inspector who is currently president of the Institute for Science and International Security.

"The real lesson of Osirak," he says, "is that if you hit one of these sites you energize the country to work covertly to obtain nuclear weapons."

Albright says that's what happened in Iraq, which responded by pumping billions of dollars into a covert weapons program that escaped international detection until after the Gulf war. By that time, Saddam was "poised to create a huge arsenal" of nuclear weapons, he said.

Gary Sick, the Iran specialist at Columbia, noted that under the Non-Proliferation Treaty of 1970 Iran is legally entitled to build facilities for a full nuclear fuel cycle, including uranium enrichment plants and plants for reprocessing spent nuclear fuel that could be used to produce weapons-grade uranium or plutonium.

"They are going about this very systematically, and very rapidly," Sick said. "What's worrisome is that there is no serious debate about this in Iran. The reformers aren't up in arms. There is, in fact, quite a bit of unanimity" that Iran, given its geography, needs to go the nuclear-weapons route.

At the American Enterprise conference last week the same point was stressed by Bernard Hourcade, a specialist on Iran at the Centre National de la Recherche Scientifique in Paris.

"The best way to keep Iran from going nuclear is to keep the mullahs" in power, he quipped. "The democrats are just as nationalistic, and a lot more efficient."