The study released by the Centre for Strategic and International Studies (CSIS), obtained by Reuters on Sunday, said Saudis made up just 350 of the 3000-strong foreign fighters in Iraq - fewer than many officials have assumed.
"Analysts and government officials in the US and Iraq have overstated the size of the foreign element in the Iraqi insurgency, especially that of the Saudi contingent," it said.
Non-Iraqi fighters made up less than 10% of the armed groups' ranks - perhaps even half that - the study said.
The report also went on to say Saudi fighters showed few signs of militancy before the US-led overthrow of Saddam Hussein, according to detailed study based on Saudi intelligence reports.
Not terrorist sympathisers
Most were motivated by "revulsion at the idea of an Arab land being occupied by a non-Arab country", the report said.
The study by Middle East analyst Anthony Cordesman and Saudi security adviser Nawaf Obaid may offer further fuel to critics who say that instead of weakening al-Qaida, the 2003 invasion of Iraq brought fresh recruits to Osama bin Laden's network.
It said Saudi Arabia had interrogated dozens of Saudi "militants" who either returned from Iraq or were caught at the border. "One important point was the number who insisted that they were not militants before the Iraq war," it said.
Foreign fighters are suspected of
being behind some bombings
"The vast majority of Saudi militants who entered Iraq were not terrorist sympathisers before the war, and were radicalised almost exclusively by the coalition invasion," the study said.
Backing up their claim, 85% of those interrogated were not on any watch list of known "militants", the study said.
Most came from the west, south or centre of Saudi Arabia, often from middle class families of prominent conservative tribes.
Many were well-educated and had jobs and all of them were Sunni Muslims, the study said.
Foreign fighters are just one element of a bloody two-year conflict in Iraq where in the last week alone more than 200 Iraqis were killed.
"Analysts and government officials in the US and Iraq have overstated the size of the foreign element in the Iraqi insurgency, especially that of the Saudi contingent"
Centre for Strategic and
On Friday, a Saudi man wearing an explosives-laden belt was arrested after another bomber blew himself up in Baghdad.
Other analysts have higher estimates for Saudi fighters in Iraq, saying that postings on Islamist websites suggested they carried out most of the attacks by foreigners, and that several thousand Saudis may have gone to Iraq.
But those numbers may be inflated because Saudi fighters receive disproportionate attention, partly because of greater media coverage and partly because they are prized volunteers who bring funds with them up to $15,000, CSIS said.
Saudi Arabia, which is also fighting domestic violence by supporters of Saudi-born bin Laden, has come under scrutiny since the 11 September 2001 attacks in the United States which were carried out by mainly Saudi hijackers.
Critics accuse the government of turning a blind eye to fighters as long as their targets were outside the kingdom.
But Saudi measures to seal the border with Iraq and its detention of preachers supporting jihad had helped curb Saudi and other fighters heading to Iraq, CSIS said.
The study estimated that the largest foreign contingent was made up of 600 Algerian fighters. It said about 550 Syrians, 500 Yemenis, 450 Sudanese, 400 Egyptians, 350 Saudis, and 150 fighters from other countries had crossed into Iraq to fight.