In an open letter condemning the Bush administration's foreign policy, the international group of experts called for a change of course.
The letter from the non-partisan Security Scholars for a Sensible Foreign Policy comprising mostly scholars from universities in countries such as Britain, Sweden, the Netherlands, Canada, Argentina and the US - including former Pentagon and US department of state staff - was released on Tuesday.
It pointed to what it described as a series of blunders in Iraq, Afghanistan and elsewhere.
"We judge that the current American policy centred around the war in Iraq is the most misguided one since the Vietnam period, one which harms the cause of the struggle against extreme Islamic terrorists," the letter said.
It said the war had distorted "public debate on foreign and national security policy with an emphasis on speculation instead of facts, on mythology instead of calculation and on misplaced moralising over considerations of national interest".
"The results of this policy have been overwhelmingly negative for US interests," it added.
"We're advising the administration, which is already in a deep hole, to stop digging"
Professor Richard Samuels, MIT
"We're advising the administration, which is already in a deep hole, to stop digging," said Professor Richard Samuels of the Massachusetts Institute of Technology.
The man who first thought to write the letter, Dr Stuart Kaufman, political science professor at the University of Delaware, said the group wanted to influence the public debate, not endorse one presidential candidate over the other for the November US elections.
"The part of it that's news is that the overwhelming consensus among national security experts is that the current policy is not working," he said. "And the people who signed this are usually people who don't agree on anything."
The US did not send enough troops to Afghanistan to fight al-Qaida, and the focus on Iraq diverted much needed resources from Afghanistan.
Among other things, the scholars said:
Some of the reasons cited by the Bush administration to go to war against Iraq were later proven wrong, including by government agencies. They include the claim that Iraq had weapons of mass destruction.
The administration did not commit enough troops to Iraq, created a security vacuum by disbanding the Iraqi army, and embarked on a poorly planned reconstruction effort.
American actions in Iraq have increased the popularity of al-Qaida in some countries and attracted recruits.
The group added: "Even on moral grounds, the case for war was dubious: The war itself has killed over a thousand Americans and unknown thousands of Iraqis. And if the threat of civil war becomes reality, ordinary Iraqis could be even worse off than they were under Saddam Hussein."