BAGHDAD, Iraq - U.S. and Iraqi officials have long believed that foreign fighters infiltrating Iraq through its porous borders with Syria, Iran and Saudi Arabia are behind most suicide missions, and the recent wave of bloody strikes has confirmed that thinking.

Authorities have found little evidence that Iraqis have been behind the near-daily stream of suicide attacks over the past six months, U.S. and Iraqi intelligence officials said, speaking on condition of anonymity because of the subject's sensitivity.

The key role of foreign fighters in suicide attacks is one reason many senior military officials, including the top U.S. general in the Middle East, tend to view the war in Iraq as slowly developing into an international struggle against militant Islam.

Iraqis have carried out less than 10 percent of more than 500 suicide attacks since 2003, according to one defense official. At least 213 attacks have occurred this year - 172 by vehicle and 41 by bombers on foot - according to a count by The Associated Press.

While most suicide attackers in Iraq are thought to be Gulf Arabs, North Africans are also streaming in to carry out deadly missions, U.S. and Iraqi officials say.

The bombers are recruited from Sunni communities, smuggled into Iraq from Syria after receiving religious indoctrination, and then quickly bundled into cars or strapped with explosive vests and sent to their deaths, the officials told the AP. The young men are not so much fighters as human bombs - a relatively small but deadly component of the Iraqi insurgency.

The trend doesn't mean Iraqis aren't part of the bloody insurgency: On the contrary, Iraqi insurgents are thought to be responsible for much of the violence and fighting in the country, although most of those are non-suicide attacks.

The military brass say Islamic extremists like Abu Musab al-Zarqawi and his al-Qaida in Iraq organization are determined to start a civil war in Iraq by attacking Iraqi security forces and members of the country's Shiite majority.

Overall, the number of foreign fighters coming into the country seems to be on the rise, compared to six months ago,

U.S. Gen. John Abizaid

said.

The majority of foreign bombers in Iraq are believed to come from countries in the Persian Gulf, mainly Saudi Arabia and Yemen as well as Jordan, U.S. officials say. They say many are transported to Syria and then smuggled into Iraq, mostly overland through Qaim - a frontier city in Iraq's western desert.

U.S. Marines taking part in a major operation around Qaim on June 20 found foreign passports and one roundtrip air ticket from Tripoli, Libya, to Damascus, Syria. They also found two passports from Sudan, two from Saudi Arabia, two from Libya, two from Algeria and one from Tunisia.

Robert Baer, a CIA officer from 1976 to 1997 who spent the much of his career in the Middle East, recently returned to the region for a month to study suicide bombers as part of an investigation for Britain's Channel 4. His trip included a 10-day visit to predominantly Shiite Iran.

Baer said Sunni Arabs who take carry out suicide attacks feel Shiites are attacking Sunnis in Iraq. "They look at the war in Iraq as an attack on Sunni Islam, not Iraq, not Saddam," he said.

In interviews while visiting prisons, terror groups and government officials, he was told that there are so many suicide bombers coming out of the Persian Gulf states that the loose networks that deploy jihadist martyrs - many run through mosques - are turning away potential attackers.

He said the mentality is: "They have taken what is ours and they will take more if we don't stop them."