BAGHDAD, Iraq – American and Iraqi forces in the western province of Anbar have seized thousands of pounds of explosives and arrested dozens of suspected insurgents in a three-day sweep that has encountered little resistance and received widespread cooperation from local residents, military officials said yesterday.

The thrust by about 1,000 U.S. Marines, soldiers, and sailors and 100 Iraqi troops, called Operation Sword, centered on towns along the Euphrates River about 90 miles west of Baghdad. Marine spokesmen have said the operation, like other recent sweeps farther west, is aimed at driving insurgents out of towns and disrupting their ability to move guerrillas, weapons, and supplies from neighboring Syria into western Iraq and other parts of the country.

“Since the combined force of Marines and soldiers entered the city of Hit on Tuesday, there has been no significant resistance or opposition,” the operations officer with the Marines’ Regimental Combat Team 2, Lieutenant Colonel Christopher Starling, said. “The people have been overwhelmingly receptive and have assisted coalition and Iraqi solders in locating roadside bombs and weapons caches.”

A Marine statement said there had been no fighting reported yesterday, no buildings destroyed, and no air strikes conducted.

The combined American and Iraqi forces have searched hundreds of homes and businesses, according to witnesses, some of whom expressed gratitude for the operation.

Iraqi army Captain Hussein Abbas said about two tons of explosives had been confiscated in Hit and that 45 suspects had been arrested, including foreigners from Saudi Arabia, Jordan, and Syria.

Iraqi and American officials say would-be insurgents from Europe, Africa, and Asia have been entering Iraq through Syria. They have accused the Syrian government of allowing the guerrillas to undergo training in Syria and move across its borders.

In Baghdad yesterday, the American military’s chief spokesman in Iraq, Air Force Brigadier General Donald Alston, said: “These borders are porous, and it requires more than just posting guards on the Iraqi side of the border. It requires support from Iraq’s neighbors, and the Iraqi government has petitioned all of its neighbors to do more to secure their borders.”

General Alston told reporters the military estimated that foreigners accounted for roughly 5% of an insurgency believed to number between 15,000-20,000. But General Alston said many of these fighters were “folks that don’t choose to fight every day.” The core of the insurgent movement measured “more in the hundreds,” he said.

The insurgents – Iraqis and foreigners alike – are overwhelmingly Sunni Muslim Arabs. Iraqi leaders have repeatedly emphasized the importance of undercutting the violence by drawing Iraqi Sunnis into a political process that is so far dominated by Shiite Muslims and ethnic Kurds.

On Wednesday, a former Iraqi electricity minister, Aiham Alsammarae, announced that he had formed a Sunni political organization whose members would include some Iraqis with links to insurgent groups.

Yesterday, however, three insurgent groups – the Ansar al-Sunna Army, the Mujaheddin Army, and the Islamic Army in Iraq – distributed a statement at a mosque in Hit saying they were not involved with Mr. Alsammarae’s organization and had not taken part in talks with American or Iraqi officials. The statement threatened Mr. Alsammarae with death.