THE IRAN PLANS.

The Bush Administration, while publicly advocating diplomacy in order to stop Iran from pursuing a nuclear weapon, has increased clandestine activities inside Iran and intensified planning for a possible major air attack. Current and former American military and intelligence officials said that Air Force planning groups are drawing up lists of targets, and teams of American combat troops have been ordered into Iran, under cover, to collect targeting data and to establish contact with anti-government ethnic-minority groups. The officials say that President Bush is determined to deny the Iranian regime the opportunity to begin a pilot program, planned for this spring, to enrich uranium.

American and European intelligence agencies, and the International Atomic Energy Agency (I.A.E.A.), agree that Iran is intent on developing the capability to produce nuclear weapons. But there are widely differing estimates of how long that will take, and whether diplomacy, sanctions, or military action is the best way to prevent it. Iran insists that its research is for peaceful use only, in keeping with the Nuclear Non-Proliferation Treaty, and that it will not be delayed or deterred.

There is a growing conviction among members of the United States military, and in the international community, that President Bush's ultimate goal in the nuclear confrontation with Iran is regime change. Iran's President, Mahmoud Ahmadinejad, has challenged the reality of the Holocaust and said that Israel must be "wiped off the map." Bush and others in the White House view him as a potential Adolf Hitler, a former senior intelligence official said. "That's the name they're using. They say, 'Will Iran get a strategic weapon and threaten another world war?' "

A government consultant with close ties to the civilian leadership in the Pentagon said that Bush was "absolutely convinced that Iran is going to get the bomb" if it is not stopped. He said that the President believes that he must do "what no Democrat or Republican, if elected in the future, would have the courage to do," and "that saving Iran is going to be his legacy."

One former defense official, who still deals with sensitive issues for the Bush Administration, told me that the military planning was premised on a belief that "a sustained bombing campaign in Iran will humiliate the religious leadership and lead the public to rise up and overthrow the government." He added, "I was shocked when I heard it, and asked myself, 'What are they smoking?' "

The rationale for regime change was articulated in early March by Patrick Clawson, an Iran expert who is the deputy director for research at the Washington Institute for Near East Policy and who has been a supporter of President Bush. "So long as Iran has an Islamic republic, it will have a nuclear-weapons program, at least clandestinely," Clawson told the Senate Foreign Relations Committee on March 2nd. "The key issue, therefore, is: How long will the present Iranian regime last?"

When I spoke to Clawson, he emphasized that "this Administration is putting a lot of effort into diplomacy." However, he added, Iran had no choice other than to accede to America's demands or face a military attack. Clawson said that he fears that Ahmadinejad "sees the West as wimps and thinks we will eventually cave in. We have to be ready to deal with Iran if the crisis escalates." Clawson said that he would prefer to rely on sabotage and other clandestine activities, such as "industrial accidents." But, he said, it would be prudent to prepare for a wider war, "given the way the Iranians are acting. This is not like planning to invade Quebec."