The 10-hour session brought together Iraqis from most parts of the country and most religious and ethnic factions. The national conference is to decide whether Iraq will adopt a leadership council or a single head of state, the Bush administration's envoy, Zalmay Khalilzad, said afterward. He was co-chairman of the meeting.

None of the major candidates to lead the transitional government — including the former exile Ahmad Chalabi, who is a favorite of the Pentagon — attended the meeting.

Their absence was an effort to prevent "too much grandstanding," but they would almost certainly be present at the national conference, an allied official said. Members of Shiite clerical groups were present and clearly visible with their turbans and flowing black gowns.

The Supreme Council for the Islamic Revolution in Iraq, a group with strong ties to Iran that boycotted a smaller meeting in Nasiriya two weeks ago, was invited, and members were believed to be present, the organizers said. A few miles from the conference hall, however, several thousand protesters affiliated with a Shiite theological college in the holy city of Najaf denounced the meeting as unrepresentative of religious Shiism.

Mr. Khalilzad said the meeting had voted to refer to a new Iraqi governing body that will be chosen in a month as a transitional government, rather than an interim authority, a phrase coined by the Bush administration. The national conference to select this government would be held in Baghdad.

The extraordinarily tight security for today's gathering — a perimeter was established a mile or so away by American forces — gave the meeting an air of disconnection with the rest of Baghdad, where workers are yet to be paid and the police are yet to appear on the streets. Some of the participants who drove from distant places in the countryside had trouble getting through the roadblocks. 

One of the reasons security was tight was that large-scale demonstrations were expected to mark Saddam Hussein's 66th birthday.

About 50 men and boys, mostly from the Tikrit area, piled into pickups and drove down Highway 1 around midday, firing guns into the air to celebrate Mr. Hussein's birthday. The men, mostly farmers, carried an array of modern weapons, including heavy machine guns and assault rifles, and the young men sprayed their bullets across the sun-baked plains north of Baghdad.

"Saddam is all we have known," Adel Ahmed, 21, said between celebratory bursts of his Kalashnikov. "We will not be apart from Saddam for the rest of our lives, I tell you." 

Amid the booms of a heavy machine gun, the men climbed back into their trucks and zoomed toward Baghdad. 

In Tikrit and nearby Awaja, Mr. Hussein's hometown, the demonstrations that members of Mr. Hussein's family had called for were thwarted by a stepped-up presence of American troops. Only two nights ago, a pro-Hussein demonstration in Tikrit left one Iraqi man injured and three Iraqi cars crushed by American tanks. 

But today, anticipating trouble, the Americans fanned out across Tikrit, setting up checkpoints and searching virtually every car that came down the road. Armored personnel carriers rumbled down the city streets and Apache attack helicopters crisscrossed the skies. The Americans imposed a 10 p.m.-to-6 a.m. curfew. 

If the actions were intended as a show of force, they worked; demonstrations that had been planned for the day fizzled out. 

"Wherever we see a crowd, we disperse it," Capt. William Kahmann said. "What we tell them is, we want you to form a new government, then we can leave." 

The graffiti in Tikrit told the story. On walls and buildings across the town, President Bush and the United States were denounced, often in vulgar language and often in English. But the Americans responded in kind. In many places, Mr. Bush's name, where it was followed by an obscenity, had been crossed out and replaced with "Saddam." 

At the Baghdad meeting, which was described afterward by participants as lively and at times emotional, eight points were adopted, including a demand for the allied forces to do more to improve security. Several Iraqis who attended the mostly closed-door sessions said the breakdown in law and order was as much on people's minds as the country's political future.

A proposal that the coalition forces should gather all personal arms from the Iraqi people was voted down in the meeting, with opponents saying they needed their weapons to protect themselves. 

In an opening address, the American administrator of Iraq, Jay Garner, a retired lieutenant general, acknowledged that ways had to be found to improve security. "Before we begin the reconstruction successfully, we have to have security," he said. "It is very difficult but we will make it happen." 

A British Foreign Office official, Mike O'Brien, the minister of state for foreign affairs, sat next to Mr. Khalilzad during the proceedings today. From the Bush administration, Larry Di Rita, the chief of staff for Secretary of Defense Donald H. Rumsfeld, was also present, as was General Garner's press secretary, Margaret Tutwiler. 

The proceedings today showed the Bush administration's dilemma. Administration officials say they see the urgent need to set up a transitional government to satisfy the clamor by Iraqis for Iraqi rule, but they also say that organizing a legitimate body quickly in the postwar disarray is very difficult. Precarious travel and unreliable telephone service complicate matters, as do procedural difficulties.

An overriding concern for Iraqis who lived under the rule of Mr. Hussein is the role of the exiles who often appear to Iraqi citizens as coming back to the country to grab power. 

At a London conference held under the aegis of the Bush administration in December, a council was formed that consisted mostly of exiles and some representatives from the Kurdish enclaves in northern Iraq. A meeting of exiles was also held in the northern town of Salhaddin this year. 

An effort will be made in the next few weeks to meld that council with Iraqi citizens from inside the country, American officials said.

While Iraqis gathered to piece together their government, others worked to replace missing pieces of their cultural heritage. Heeding the American call for information on looted artifacts, Iraqis have delivered some antiquities to American forces and passed on tips about the whereabouts of others. As a result, more than 100 treasures, including a 7,000-year-old vase, have been returned, the United States Central Command said today.