Although Bush administration officials have frequently lashed out at Syria and Iran, accusing it of helping insurgents and militias here, the largest number of foreign fighters and suicide bombers in Iraq come from a third neighbor, Saudi Arabia, according to a senior U.S. military officer and Iraqi lawmakers.

About 45% of all foreign militants targeting U.S. troops and Iraqi civilians and security forces are from Saudi Arabia; 15% are from Syria and Lebanon; and 10% are from North Africa, according to official U.S. military figures made available to The Times by the senior officer. Nearly half of the 135 foreigners in U.S. detention facilities in Iraq are Saudis, he said.