However, new explosions were heard later Thursday as U.S. warplanes circled over the city. The significance of that new action was unclear.
Elsewhere, 10 U.S. soldiers were killed Thursday — eight of them in a car bombing south of Baghdad. Two were killed in a convoy attack in Baghdad and roadside bomb in Baqoubah, north of the capital.
The Fallujah deal came after intense international pressure on the United States to find a peaceful solution to the standoff that killed hundreds of Iraqis and became a symbol of anti-U.S. resistance in Iraq, fueling violence that made April the deadliest month for American forces.
Only last week, U.S. commanders threatened to launch an all-out attack on the city to root out an estimated 1,500 Sunni insurgents inside. Even after Washington decided to push ahead with political efforts instead, Marines and guerrillas continued to clash, with the heavy U.S. bombardment of the city the past two nights televised around the world.
In other developments:
"I can't say this is the only group out there," the official said. "These guys are the most sophisticated."
When the fall of Saddam's regime was imminent, the officers dispersed to cities around Iraq. They are working largely without coordination with one another, but are believed to be guiding some of the anti-U.S. forces in Fallujah, the official said.
The deal in Fallujah was reached after talks involving several parties, including U.S. officials and local leaders, reports CBS News' Lisa Barron.
The move came after three days of intense violence in Fallujah, despite U.S. attempts to maintain a cease-fire. On Tuesday night, warplanes and helicopter gunships struck guerrilla positions, raising fires and plumes of smoke over the city. Throughout the day Wednesday, insurgents attacked Marines in several neighborhoods, and U.S. forces responded by pounding the city with 500-pound bombs.
U.S. Marines encircled the city of 200,000 on April 5, following the killings and mutilations of four U.S. contract workers on March 31. In addition to the hundreds of Iraqis killed, at least eight Marines died in the fighting.
The agreement provides for a new force, known as the Fallujah Protective Army, to enter the city Friday and provide security. It will consist of up to 1,100 Iraqi soldiers led by a former general from Saddam's military, Lt. Col. Brennan Byrne said.
Marine forces will pull back from their positions in and around Fallujah, while the FPA forms a new cordon around it and then moves into the city, Byrne said.
Byrne said the Marines would remain around the Fallujah area, but not in an immediate cordon or inside the city, and the FPA will be subordinate to the Marine 1st Expeditionary Force.
He identified the commander of the FPA only as Gen. Salah, a former division commander under Saddam. Many of the guerrillas in Fallujah are believed to be former members of Saddam's regime or military.
Byrne did not know the general's full name. But a Lt. Gen. Salah Abboud al-Jabouri, a native of the Fallujah region, served as governor of Anbar province under Saddam and was a senior commander in Saddam's military.
The bombing that killed eight U.S. soldiers from the Army's 1st Armored Division occurred near the town of Mahmoudiyah, south of Baghdad, the military said. Four wounded soldiers were taken to the 31st Combat Support Hospital in Baghdad.
The slain soldiers were to have returned to their home base in Germany by now, under their original deployment orders. After this month's surge in violence, the division's departure was blocked by the Pentagon and the unit was ordered to remain in Iraq for 90 days.
Another soldier died in eastern Baghdad, and a roadside bomb felled another GI north of the capital.
The deaths raised to 126 the number of U.S. troops killed in combat in April, the bloodiest month for U.S. forces in Iraq. The military said another soldier died in a vehicle accident in western Baghdad.
At least 736 U.S. troops have died in Iraq since the war began in March 2003. Up to 1,200 Iraqis also have been killed this month.
In southern Iraq, witnesses reported that Shiite militiamen clashed Thursday with U.S. troops at a base in the holy city of Najaf. There were no immediate details on the clashes. Earlier, militiamen fired seven mortars at the base, causing no casualties.