WASHINGTON, Jan. 5 — President Bush's national security team is assembling final plans for administering and democratizing Iraq after the expected ouster of Saddam Hussein. Those plans call for a heavy American military presence in the country for at least 18 months, military trials of only the most senior Iraqi leaders and quick takeover of the country's oil fields to pay for reconstruction.

The proposals, according to administration officials who have been developing them for several months, have been discussed informally with Mr. Bush in considerable detail. They would amount to the most ambitious American effort to administer a country since the occupations of Japan and Germany at the end of World War II. With Mr. Bush's return here this afternoon, his principal foreign policy advisers are expected to shape the final details in White House meetings and then formally present them to the president.

Many elements of the plans are highly classified, and some are still being debated as Mr. Bush's team tries to allay concerns that the United States would seek to be a colonial power in Iraq. But the broad outlines show the enormous complexity of the task in months ahead, and point to some of the difficulties that would follow even a swift and successful removal of Mr. Hussein from power, including these:

¶Though Mr. Bush came to office expressing distaste for using the military for what he called nation building, the Pentagon is preparing for at least a year and a half of military control of Iraq, with forces that would keep the peace, hunt down Mr. Hussein's top leaders and weapons of mass destruction and, in the words of one of Mr. Bush's senior advisers, "keep the country whole."

¶A civilian administrator — perhaps designated by the United Nations — would run the country's economy, rebuild its schools and political institutions, and administer aid programs. Placing those powers in nonmilitary hands, administration officials hope, will quell Arab concerns that a military commander would wield the kind of unchallenged authority that Gen. Douglas MacArthur exercised as supreme commander in Japan.

¶Only "key" senior officials of the Hussein government "would need to be removed and called to account," according to an administration document summarizing plans for war trials. People in the Iraqi hierarchy who help bring down the government may be offered leniency.

¶The administration plan says, "Government elements closely identified with Saddam's regime, such as the revolutionary courts or the special security organization, will be eliminated, but much of the rest of the government will be reformed and kept."

¶While publicly saying Iraqi oil would remain what one senior official calls "the patrimony of the Iraqi people," the administration is debating how to protect oil fields during the conflict and how an occupied Iraq would be represented in the Organization of Petroleum Exporting Countries, if at all.

¶After long debate, especially between the Pentagon and the State Department, the White House has rejected for now the idea of creating a provisional government before any invasion.

Officials involved in the planning caution that no matter how detailed their plans, many crucial decisions would have to be made on the ground in Iraq. So for now they have focused on legal precedents — including an examination of the legal basis for taking control of the country at all — and a study of past successes and failures in nation building, reaching back to the American administration of the Philippines after the Spanish-American War.

The plans presented to Mr. Bush will include several contingencies that depend heavily, officials say, on how Mr. Hussein leaves power. "So much rides on the conflict itself, if it becomes a conflict, and on how the conflict starts and how the conflict ends," one of Mr. Bush's top advisers said.

Much also depends on whether the arriving American troops would be welcomed or shot at, and the Central Intelligence Agency has been drawing up scenarios that range from a friendly occupation to a hostile one.

Yet under all of the possibilities, the American military would remain the central player in running the country for some time. The Pentagon has warned that it would take at least a year to be certain that all of Mr. Hussein's weapons stores were destroyed.

Notably, the administration's written description of its goals include these two objectives: "preserve Iraq as a unitary state, with its territorial integrity intact," and "prevent unhelpful outside interference, military or nonmilitary," apparently a warning to neighboring countries.

Administration officials insist American forces would not stay in Iraq a day longer than is necessary to stabilize the country.

"I don't think we're talking about months," one of Mr. Bush's top advisers said of the planned occupation. "But I don't think we're talking a lot of years, either."

The Command
Military Joined
With Civilian

When administration officials first began publicly discussing the idea of an American military administration for Iraq, the reaction in the Arab world was swift: The Arabs wanted no American Caesar in Iraq, no symbol of a colonial governor. "The last thing we need," a senior official said, in an allusion to General MacArthur, "is someone walking around with a corncob pipe, telling Iraqis how to form a government."

As a result, the steering group on Iraq policy is now discussing a hybrid command with an American military commander in charge of security and some kind of civilian administrator — of theoretically equal influence — to get the schools running, the oil fields pumping and the economy jump-started. It is not clear whether that administrator would be an American or if the United Nations would take the lead in that part of the operation.

It is widely assumed that in the first chaotic months, the military commander will have unquestioned authority. "Remember, you will have decapitated the command and control for the Iraqi military forces," a senior official said. "Who is going to make sure that score-settling does not break out, that there is not fights between the various ethnic communities? It is going to have to be the U.S. military for some period of time, and if there is a military command, there will certainly be a military commander."

But the handover of more and more responsibility from the military administration to an international civilian administration — and several years down the road to an Iraqi-run government — is still murky. Officials, referring to the ruling Baath Party, say "de-Baathification" of the nation will be at least as complex as de-Nazification was in Germany.

"We know one thing," said a diplomat involved in the planning. "Things will have to come together a lot faster than they have in Afghanistan."

The Oil
Protecting It
For the Iraqis

There is no more delicate question for the administration than how to deal with Iraq's oil reserves — the world's second largest, behind Saudi Arabia's — and how to raise money from oil sales for rebuilding without prompting charges that control of oil, not disarming Iraq, is Mr. Bush's true aim.

Administration officials have been careful always to talk about Iraqi oil as the property of the Iraqi people. But in the White House, the major concern is that Mr. Hussein may plan to destroy the oil infrastructure in the first days of any war, while trying to make it appear as if the destruction was the work of American forces.

"What happens if he started systematically destroying the fields?" a senior official said. "It's a big source of concern, and we are trying to take account of it as we plan how to use our military forces."

Secretary of State Colin L. Powell, speaking on Dec. 29, hinted at such a military plan when he said, "If coalition forces go into those oil fields, we would want to protect those fields and make sure that they are used to benefit the people of Iraq, and are not destroyed or damaged by a failing regime on the way out the door."

The White House has already concluded that the United Nations' oil-for-food program, under which Iraq is permitted to sell a limited amount of oil to buy civilian goods, will have to be amended quickly so oil revenues can be used more broadly in the country. But it is unclear how the administration plans to finesse the question of Iraq's role in OPEC and who would represent occupied Iraq at the organization's meetings.

The administration is already anticipating that neighboring Arab nations may accuse occupied Iraq of pumping oil beyond OPEC quotas. One official said Washington "fully expects" that the United States will be suspected of undermining the oil organization, and it is working on strategies, which he would not describe, to allay those fears.

The Leadership
Planning Both Trials
And Incentives

Mr. Bush has been warning since October that Iraqi generals who obeyed any orders to use chemical or biological weapons against American troops would be punished, perhaps as war criminals.

Now, as part of the effort to undermine Mr. Hussein's government and get evidence that has so far eluded United Nations inspectors, the White House is putting a slightly different spin on that kind of talk.

Those who have helped build Mr. Hussein's weapons stockpile, officials say, may win some redemption by helping inspectors — and American forces.

That approach appears to be part of a strategy to encourage a coup and persuade military leaders and scientists to give up the country's chemical and biological stockpiles and its nuclear research efforts. "The politics of Iraq are so opaque that it's just hard to know what is or isn't rumbling under the surface," one of Mr. Bush's most senior advisers said. As a result, the president is looking to create "maximum pressure" on the top leadership.

Already the C.I.A. and others have drawn up lists of Mr. Hussein's top command and the heads of his security forces who would probably be put on trial.

One State Department working group is studying a kind of "truth and reconciliation" process, modeled after the one in South Africa, which could publicly shame, but not necessarily punish, human rights violators.

The Transition
No to Installing
Provisional Rulers

Few issues have divided the administration more bitterly than how to create a transitional Iraqi government that could serve as a bridge between the American military occupation and a permanent, democratic government. The issue reflects the administration's ideological fault lines, and in recent months Mr. Bush's national security adviser, Condoleezza Rice, has stepped in, as one senior aide said, "to make sure there was not a public food fight on this one."

White House officials say that those divisions have now been resolved, and that while planning is going forward, the United States will not overtly install a provisional government or designate its leaders.

The division was a familiar one. Senior civilian officials in the Pentagon and some advisers to Vice President Dick Cheney argued for the creation of a provisional government even before Baghdad falls. It would be led, at least initially, by Iraqi exiles. The proponents argue that such a government in exile would speed creation of a permanent government if Mr. Hussein is removed, allowing United States forces to withdraw sooner. Among the reported advocates were Secretary of Defense Donald H. Rumsfeld, who wants the military's role to be brief.

"The quicker you get a transition from military victory to transitional government, the better," a senior Pentagon official said. "We want to be there as long as necessary, but as short as possible."

On the other side of the debate are advocates of giving more power to Iraqis now living in Iraq. These advocates, mainly in the State Department and C.I.A., say the Iraqi exiles have no legitimacy among the Iraqi people. One proposal favored by State Department officials calls for having an international civilian agency, advised by Iraqis and protected by allied peacekeeping forces, run the nation while Iraqis elect local governments, create a new constitution and eventually select a national legislature, somewhat along the postwar model of Afghanistan.

The White House has tried to finesse those differences by saying it favors a government formed by "free Iraqis" both inside and outside Iraq.

But inside the Pentagon there are doubts. "The argument that you have to leave seats at the table for people inside Iraq has one problem: there is no one inside," said a senior official who supports the Iraqi National Congress.

An official close to Mr. Bush acknowledged that "there are not a lot of free Iraqis inside Iraq." Pausing, he added, "But there will be."