The conflict in Iraq is evolving into an ideal training ground for a new breed of seasoned urban terrorist capable of striking anywhere in the world, according to security and terrorism analysts.
The hard core of combatants in the anti-American jihad, whether foreign or Iraqi, are potentially more mobile and dangerous than the fearsome Muhajedeen fighters who drove the Soviet Union out of Afghanistan in the 1980s and who, not incidentally, gave rise to Osama bin Laden's Al-Qaeda, they say.
"It is a perfect model of urban combat that did not exist in Afghanistan," said Michael Klare, a professor and security expert at the University of Amherst in the United States.
Foreign fighters "will come back from Iraq with an ability to do terrible things. The longer the war goes on, the more people will be trained in this fashion, and the more of a danger they will pose," he said.
The anti-American forces in Iraq are fighting street-by-street and building-by-building, using improvised explosive devices, sniper fire and suicide bombers, techniques that would all be "applicable and dangerous in a European urban setting," he added.
US government analysts have also identified a growing risk of exportable urban warfare.
"Iraq may prove to be an even more effective training ground for Islamist extremists than Afghanistan was in Al-Qaeda's early days because it is serving as a real-world laboratory," according to a classified CIA report cited last year by the New York Times.
Most jihadist fighters in Iraq are not grouped in camps, where they would be vulnerable, but move individually or in small groups through an elaborate urban network of safe houses, according to Iraqi police, the US military and the testimony of captured combatants.
By operating in this manner they gain deadly experience in clandestine and guerrilla urban warfare.
Jeremy Binnie, a conflict analyst at Jane's Defence Weekly, also highlighted the contrast with Afghanistan which, he said, "was more appropriate to train fighters for Bosnia or Chechnya. It was a traditional guerrilla tactic - you retreat to your mountainous safe haven."
"In Iraq it is much more about using safe houses, smuggling things underneath the noses of security forces, and developing bombing tactics and targeting technologies relevant to an urban terrorist campaign," he said.
As for the possibility that anti-American forces may one day venture beyond Iraq's borders, Binnie was more circumspect.
"So far, people are fighting inside Iraq, and that movement abroad does not seem to have started. But it is something all security forces are extremely concerned about," he said.
"What we are more worried about are the more senior figures who are doing the training and developing the skills," he added. "We are probably not talking about a huge number of people - probably more hundreds than thousands."
Klare, who published a prophetic article in 2003 entitled "How to defeat bin Laden," was not optimistic that leaders in Washington would act to prevent the Iraqi resistance from evolving into a highly-mobile network of urban terrorism.
"The professionals in the State Department, Defense Department and the CIA understand this very well. But it does not seem to affect decision-making in the White House, that has done everything wrong from the beginning."