FALLUJAH, Iraq -- A dozen former Iraqi generals and intelligence officers met Friday with U.S. military leaders and pledged to lead a brigade of up to 1,000 Iraqi soldiers to replace the Marines fortifying this city's borders.

But U.S. military officials cautioned that the arrival of Iraqi forces in this embattled city does not necessarily mean peace. It was a warning made painfully clear when a suicide car bomb on the city's outskirts killed two Americans and wounded six.

The two deaths on the final day of April raised the U.S. death toll to 136, making it the deadliest month for American forces -- as well as for Iraqis -- since President Bush launched the war in March 2003.

Negotiations also were taking place in the southern city of Najaf, where tribal leaders and police agreed to a three-day truce as part of a plan to resolve a standoff between soldiers and militiamen loyal to radical Shiite cleric Muqtada al-Sadr.

The shift of security responsibilities to Iraqis -- with U.S. forces pulling back from most of their positions inside the city -- was a move toward ending the intense fighting that has evoked strong international criticism.

Brig. Gen. Mark Kimmitt, coalition deputy operations chief, insisted the Marines were not "withdrawing" from Fallujah, but were simply "repositioning." Asked if the Marines were leaving, Kimmitt replied, "Nothing could be further from the truth."

Choosing his words carefully while describing the new arrangement that other officials Friday called "delicate," Marine Col. John Toolan said Friday that the transition will take some time.

"I've been saying all along that this was all about leadership," Toolan said following a 30-minute meeting with former military leaders of deposed Iraqi President Saddam Hussein. "And, finally, we've got someone stepping up."

That someone is Maj. Gen. Jassim Mohammed Saleh, who will lead the newly formed 1st Battalion of the Fallujah Protection Brigade.

Saleh said his brigade, which seemed to come out of nowhere during the course of the past week, is part of the "new army of Iraq."

"We are very happy (to) cooperate with the Marines and Army," he said.

After shaking Saleh's hand and telling him they would speak again soon, Toolan said the brief meeting was meant to confirm the Iraqis' commitment to taking over the cordon around Fallujah, which thousands of Marines shed blood to establish and fought hard to hold for nearly a month.

Toolan said he was confident in the generals and their forces, but he refused to say when the troops would be in the city or when the Marines would pull back, though some troops started packing Friday.

Even while the generals talked of today's operations and reporters bantered about the sudden outbreak of peace in Fallujah, fighting continued Friday along the city's troublesome northern and western regions along the Euphrates River.

Exploding mortars, probably the same 82 mm shells that insurgents have volleyed at Marines day after day, crashed to the ground where Marine patrols have ventured in the past week.

A 15-minute firefight raged near the old bridge over the Euphrates near where four American security contractors were slain March 31. Heavy machine guns ripped away furiously for so long that Marine gunners across the river commented that their barrels were probably melting.

And late Friday afternoon, mosques broadcast military marches advocating jihad and speakers called Fallujah the "city of heroes" for battling the Marines.

Marine leaders in the field urged their men not to let their guard down, even though it looked like they would soon be pulling back.

Toolan said the arrival of Iraqi forces does not guarantee peace.

"It still remains a concern that not all the cells operating in the city are buying into their effort," Toolan said of continued fighting Thursday afternoon and night.

He and other officials said there was still much talking to do before taking action.

According to a draft statement issued Friday by I Marine Expeditionary Force officials in Fallujah, the new Iraqi force will work with the Iraqi Civil Defense Corps and Iraqi police to replace the Marines at checkpoints and strategic points along the cordon around Fallujah.

"The mission of the battalion will be to assist in returning peace and stability to the city of Fallujah, facilitate the flow of support, and foster the rapid reconstruction and employment of citizens inside the city," the statement read.

The arrangement was touted as a "new model of cooperation" that recognized the "security of Al Anbar (province) will ultimately be an Iraqi responsibility. This will be an important step in the transition from Coalition to Iraqi authority."

While the sudden development of an Iraqi force to take over Fallujah may have surprised some on the ground, where Marines have said for weeks that they were ready and poised to crush the thousand or more insurgents dug in the city at all cost, there was a growing realization among Marines and their leaders that a victory in Fallujah would have to have an Iraqi face.

"The way I look at it, it had to happen this way," said Lt. Josh Jamison, the young leader of Fox Company's 2nd Platoon, the first infantry platoon to lose a Marine during the initial cordon April 5 and the first to fight its way into the city from the northwest April 6.

"We could have attacked them and killed them all -- and, believe me, all my boys are still ready and capable of doing it," Jamison said Friday after being shown on a map the town some 10 miles from Fallujah where his 2nd Battalion, 1st Marine Regiment would soon pull back to. "And Fallujah would pretty much be in rubble. What would we have then?"

Security in Fallujah has to be something the Iraqis do for themselves, Jamison said, adding that the Marines would not be too far off if the new Iraqi forces needed help.

"This is really good because we're not really going anywhere," he said. "We're still right here. So if they mess it up or if the Iraqis need us, we're more than ready to come finish the job. I think the people of Fallujah believe that now."

Other troops occupying hard-won positions in the city at first seemed to treat the news that they might be pulling out in a matter of days with some natural skepticism. Plans change every day, they say; besides, insurgents were still shooting at them.

But by Friday evening, many seemed encouraged by the news.

"I still think we should push forward," said Lance Cpl. Ayron Kull, 20, of Niles, Mich., who was just coming off a shift monitoring the late-afternoon firefight in the city Friday.

"But maybe it's good. Let's give the Iraqis a chance. Maybe they can do it and we won't have to come back here and start all over again."

The Associated Press contributed to this report.

Staff writer Darrin Mortenson and photographer Hayne Palmour are reporting from Iraq; they are with the Marines from Camp Pendleton. Their stories and photos are collected at www.nctimes.com/military/iraq.