US: President Bush's former national security co-ordinator has warned that a military strike against Iran could be more damaging to American interests than the current conflict in Iraq has been.
Writing in the New York Times, Richard Clarke says that during the 1990s, President Bill Clinton's administration and the Pentagon considered bombing Iraq.
"But after long debate, the highest levels of the military could not forecast a way in which things would end favourably for the United States."
Mr Clarke was a national security adviser to four presidents and was Mr Bush's counter-terrorism adviser on September 11th, 2001. He resigned in 2003 and published a book, Against All Enemies, that criticised the invasion of Iraq as hampering the campaign against terrorism.
Mr Clarke warns that bombing Iran's nuclear installations "would simply begin a multi-move, escalatory process" that could see Iran responding by attacking Persian Gulf oil facilities, using terrorist networks to attack American targets worldwide and making the situation in Iraq even more dangerous.
"Iran has forces at its command that are far superior to anything al-Qaeda was ever able to field. The Lebanese terrorist organisation Hizbullah has a global reach, and has served in the past as an instrument of Iran. We might hope that Hizbullah, now a political party, would decide that it has too much to lose by joining a war against the United States. But this would be a dangerous bet," he writes.
Mr Clarke suggests that, regardless of the Iranian response, the US would seek to achieve "escalation dominance" whereby Iran would be afraid to respond in case the next round of American attacks would be too lethal for the regime to survive.
"Bloodied by Iranian retaliation, President Bush would most likely authorise wider and more intensive bombing. Non-military Iranian government targets would probably be struck in a vain hope that the Iranian people would seize the opportunity to overthrow the government. More likely, the American war against Iran would guarantee the regime decades more of control," he writes.
President Bush has dismissed reports that the administration is considering the use of tactical nuclear weapons to destroy Iran's nuclear facilities but he has consistently refused to rule out a military strike against Iran.
"The president assures us he will seek a diplomatic solution to the Iranian crisis. And there is a role for threats of force to back up diplomacy and help concentrate the minds of our allies. But the current level of activity in the Pentagon suggests more than just standard contingency planning or tactical sabre-rattling," Mr Clarke writes.
Describing the parallels with the run-up to the Iraq war "all too striking", Mr Clarke urges US legislators to ask tougher questions about Mr Bush's intentions.
"Remember that in May 2002 President Bush declared that there was 'no war plan on my desk', despite having actually spent months working on detailed plans for the Iraq invasion.
"Congress did not ask the hard questions then. It must not permit the administration to launch another war whose outcome cannot be known, or worse, known all too well," he writes.