WASHINGTON, April 11 — One of President Bush's most senior foreign policy advisers spoke with unusual candor last week about the quandary the White House faces as it tries to confront Iran.
"The problem is that our policy has been all carrots and no sticks," the adviser told a gathering of academics and outside strategists, according to members of the audience. "And the Iranians know it."
It is partly for that reason, other administration officials say, that President Bush and his aides see some benefits in the increasing public discussion about what the White House may do if diplomacy fails to persuade Iran to halt what they suspect is a nuclear weapons program.
Iran's announcement on Tuesday that it had succeeded in enriching uranium — a significant step toward building a weapon, which most experts believe is still years away — is bound to heighten the escalation of threats between Washington and Tehran.
Even before the announcement, news accounts in recent days of what airstrikes could look like, appearing in The New Yorker, The Washington Post and elsewhere, served as what one senior official called "a reminder" to the Iranian government and to Europe, Russia and China "of where this could go one day."
But at the Pentagon and elsewhere in the administration, officials say the prospect of military action remains remote in the short term and highly problematic beyond that.
The issue remains delicate within an administration that has identified Iran as a major threat. The senior adviser who spoke candidly at last week's gathering did so only under ground rules that guaranteed him anonymity, and members of the audience reported his comments on the condition that they also not be identified.
"Is it a good thing for the Iranians to think there are occasions where the U.S. would use force? Sure," said Eliot A. Cohen, a professor at Johns Hopkins University who directed the Air Force's definitive study of the first war against Iraq. "But I don't get a sense that people in the administration are champing at the bit to launch another war in the Persian Gulf."
Others suggest that the vague drumbeat of talk about military action may be less aimed at Tehran than at China and Russia — two countries that have said they oppose even the threat of economic sanctions against Iran, much less threats to set back the Iranian program by obliterating its facilities.
"In Tehran, the threat of military action is double-edged," said Ashton B. Carter, a Harvard security expert who worked on nuclear issues in the Clinton administration. "It may scare the leadership, but it could also cause people to rally around the leadership. Where it's most effective is showing the Russians and the Chinese that we are serious about stopping this program."
The question is how serious, and on that question the administration seems happy to create a strategic fog. Officials at the Pentagon say military planners are examining and updating a variety of contingencies for possible military action against Iran. But they quickly add that such updates are routine.
On Tuesday, as the Iranians were announcing that they had successfully enriched a test amount of uranium, Defense Secretary Donald H. Rumsfeld dismissed the growing tempo of reports about plans to attack Iran as a "fantasy land" and insisted that the administration was sticking to the diplomatic track in its dealings with Tehran.
Yet when asked whether he had directed the military's Joint Staff or Central Command to update or refine the contingencies the military is preparing for Iran, Mr. Rumsfeld bristled. "The last thing I'm going to do," he said, "is to start telling you or anyone else in the press or the world at what point we refresh a plan or don't refresh a plan, and why. It just isn't useful."
He said he had yet to hear expert opinion from government analysts about what Iran's declaration a few hours earlier meant.
Mr. Rumsfeld was nearly alone among administration officials in saying anything about the issue publicly. Others throughout the government, and even some outsiders who maintain close ties to those in authority, had to be promised anonymity before they would talk about the nuances of military planning.
Some officials, from a range of agencies including the Defense Intelligence Agency and the Central Command, which oversees military operations in the Middle East, said there was none of the feverish planning that took place in the prelude to the Iraq war, and no indication that the White House was seeking an explanation of its military options.
"The strike plans have been in place for some time," said one former senior Pentagon official who is in close touch with his former colleagues.
Tactically, eliminating Iran's nuclear sites, experts say, would require 600 to 1,000 air sorties to make sure that underground sites were destroyed.
Strategically, the task would be more enormous, because the United States would have to be prepared to stop Iran from interfering with oil shipments coming out of the Gulf, to cut off terrorist attacks, and to keep Iran from inciting uprisings in southern Iraq.
Secretary of State Condoleezza Rice told a foreign diplomat who visited her recently that to use military force to eliminate Iran's nuclear sites would be an extraordinarily difficult task; President Bush all but dismissed it as a near-term option to some lawmakers who, on condition of anonymity, relayed the essence of their discussion.
According to current and retired senior military officers and Pentagon officials, the military options against Iran range from a limited overnight strike by cruise missiles or stealth bombers aimed at nuclear-related activities, to a much larger series of attacks over several days against not only nuclear-related sites, but also other government targets, including the country's Revolutionary Guard and its intelligence headquarters.
Iran's large uranium-enrichment complex at Natanz, including an unfinished hall for 50,000 nuclear centrifuges that sits empty more than 50 feet underground, could be destroyed with earth-penetrating conventional bombs. Its conversion facility at Isfahan is above ground and easier to hit.
But senior officers warned that attacking targets in Iran would be much more difficult than the air campaign against Iraq in 2003. Iran's air defenses are more formidable. Many nuclear-related targets are dispersed across the country or buried deep underground. And United States intelligence analysts acknowledge that they do not know where all of Iran's secret nuclear-related activities are situated.
"Iran poses a very difficult target set," said one former top officer who was involved in target planning. "It's a bigger country, with more rugged terrain. It would be very difficult to take down."
Those officers and Pentagon officials, as well as independent military specialists, emphasized that there were no indications that airstrikes or commando attacks were imminent, and that any military action would most likely unleash a series of retaliatory strikes from Tehran.
"The consequences of U.S. strikes are enormous," concludes a new report by Anthony H. Cordesman and Khalid R. Al-Rodhan of the Center for Strategic and International Studies in Washington.
The report, released Friday, warned that Iran could retaliate by firing missiles at United States troops in Iraq and Afghanistan, by using proxy groups in Iraq to attack American soldiers there, and by sending suicide bombers to the United States.
