Dr Mohamed ElBaradei, head of the International Atomic Energy Agency, described those wanting to bomb Iranian nuclear facilities as "new crazies".
After Iraq, Dr ElBaradei said he did not want to see "another war".
He made his comments in an interview for a BBC Radio 4 documentary to be broadcast at 2000BST on Friday.
This is not the first time that Dr ElBaradei has spoken out against the possibility of using force against Iran, but it is perhaps his strongest warning to date.
Tehran is still refusing to bow to demands from the UN Security Council to halt its uranium enrichment program, which the United States fears would give it access to material for a bomb.
Dr ElBaradei said a nuclear-armed Iran would be terrible but the jury was still out as to whether the country even wanted nuclear weapons.
But he said you could not "bomb knowledge", and he was scathing towards those who still favored air strikes after the experience of intervention in Iraq.
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"I wake every morning and see 100 Iraqis innocent civilians are dying," he said. "I have no brief other than to make sure we don't go into another war or that we go crazy into killing each other. You do not want to give additional argument to new crazies who say 'let's go and bomb Iran.'"
Asked who the "new crazies" were he replied: "Those who have extreme views and say the only solution is to impose your will by force."
Dr ElBaradei said he was not referring to President George Bush but his remarks are likely to be interpreted as a swipe at those neo-conservatives in the US who still favor military action.
In the light of Iran's secretive dealings with black market nuclear suppliers he said it owed his agency a confession over its once clandestine activities.
In his latest report, last week, he said Iran continued to enrich uranium and information on its activities was now "deteriorating."
Dr ElBaradei angered the US, UK, France and Germany backing the idea that Iran should be allowed limited uranium enrichment under strict supervision.
His comments last week sparked immediate complaints from the countries.
Inside the IAEA - A year with the nuclear detectives will be broadcast BBC Radio 4, 2000 BST 31 May and 7 June 2000 BST.
© BBC MMVII