But Sunday's edition of the New York Times questioned the claims, quoting four Pentagon and administration officials as saying although the US has contingencies in place to deal with Iran's nuclear ambitions, this did not equate to military confrontation.
Investigative journalist Seymour Hersh, in Monday's issue of the New Yorker magazine, quotes former and current intelligence and defence officials as saying the US administration increasingly sees "regime change" in Tehran as the ultimate goal.
Hersh quotes an unidentified senior Pentagon adviser on the "war on terror" as saying: "This White House believes that the only way to solve the problem is to change the power structure in Iran, and that means war."
Activities stepped up
The report says the administration has stepped up clandestine activities in Iran and has initiated a series of talks on its plans with "a few key senators and members of Congress".
Hersh uncovered the My Lai massacre by US troops during the Vietnam war as well as American abuses at Iraq's Abu Ghraib prison.
"This White House believes that the only way to solve the problem is to change the power structure in Iran, and that means war"
But the New York Times says some critics see Hersh as "too eager to report assertions critical of the government that are difficult to fully substantiate".
The United States says it is focused on forging a diplomatic solution to the Iran impasse but refuses to rule out an attack to deal with what it says is one of the biggest threats to Middle East stability.
The New Yorker article cites a former senior defence official saying the military believed a sustained bombing campaign against Iran would humiliate the leadership and lead the Iranian public to overthrow it.
The report also says the US military is considering the use of a nuclear weapon to destroy Iran's main centrifuge plant at Natanz.
Hersh reports that one option involves the use of a bunker-buster nuclear weapon, such as the B61-11.
The Times of London also cites White House insiders as saying a nuclear-armed Iran is too dangerous to be left to a potential Democrat president.
ne date suggested for an attack on Iran.
But it says a strike with a conventional weapon is much more likely, possibly a 13,600-kg bunker-busting missile called the Big Blu which should be available to the US Air Force by 2008 - o
"Regardless of how bad Bush's poll numbers are, Americans love a display of firepower"
The paper adds that Bush officials believe that while it is true setbacks in Iran's neighbour, Iraq, have diminished American enthusiasm for military intervention, it would be a mistake to conclude that Americans would not stomach a strike.
"The American people are not looking for new fights but they understand the nature of the Iranian threat very clearly," the Times quotes a senior US defence official as saying.
It also points out a potential upside of a strike on Iran for US leaders George Bush and Dick Cheney, quoting American defence analyst John Pike of globalsecurity.org as saying:
"Regardless of how bad Bush's poll numbers are, Americans love a display of firepower."