With the war in Iraq winding down, U.S. military commanders plan to start sending home some warships and planes but continue building up ground troops to deal with security, humanitarian relief and reconstruction challenges, defense officials said yesterday.

Vice Adm. Timothy J. Keating, commander of U.S. and allied naval forces in the war, told reporters that two or three of the five U.S. aircraft carriers engaged in missions over Iraq will likely be dispatched soon to home ports. A senior Air Force official said that four B-2 stealth bombers have already returned to their permanent base in Missouri from the Indian Ocean island of Diego Garcia, and preparations are underway to send F-117 stealth fighters in Qatar back to the United States.

Since the fall of Baghdad last week and the collapse of Iraqi resistance in the northern cities of Mosul and Kirkuk, the number of air combat missions has waned from about 600 to 400 a day. Most now are focused on providing support for Army and Marine units closing in on Tikrit, the ancestral home of Saddam Hussein, and other operations in central Iraq.

"I think the requirement is going to decrease relatively soon, and as that decrease is realized, we'll be able to pull assets out of the theater," Keating said in a video-telecast news conference from his headquarters in Bahrain.

In contrast to the reduction in air forces, plans call for more Army troops to keep flowing into the Persian Gulf region. Elements of the 4th Infantry Division and the 3rd Armored Cavalry Regiment, recently arrived in Kuwait, have begun moving into Iraq. Next in line to deploy are the 1st Armored Division from Germany and the 1st Cavalry Division from Texas, officials said.

Worried about tensions with North Korea and other potential hot spots, Pentagon officials are eager to withdraw what forces they can from the Persian Gulf and allow them to rest and recover. At the same time, U.S. military planners recognize that a U.S. occupation force for Iraq will need to be bigger, at least for awhile, than the invasion force of about 125,000 American and British troops. Just how much larger has not been decided.

"As the situation on the ground evolves, we have decision points where we can say, 'Stop this. We don't need that,' " a senior military official said. "We just don't know yet."

Although Iraq's military and security organizations appear to have dissolved throughout the country, Pentagon officials said combat operations are likely to persist for some time as pockets of resistance are encountered in areas that U.S. ground forces have yet to sweep through.

"The thing that we're most concerned about right now is the Sunni triangle between Tikrit, Ramadi and Baquabah," the military official said, referring to an area just north of Baghdad. "We're not in there yet, except with some small forces. That's where we'd expect a fight, but we don't know."

Army and Marine elements were reported yesterday advancing north of the Iraqi capital toward Tikrit, moving along both banks of the Tigris River.

The decision on when to declare a formal end to combat operations and enter what the Pentagon calls the fourth phase of the campaign, or reconstruction, rests with Gen. Tommy R. Franks, the top U.S. commander in the region. The decision will carry some legal significance. Under the Geneva Conventions, once the fighting ends the victorious force carries certain obligations to meet the food and medical needs of the country it is occupying and to protect civilians from violence.

While U.S. forces have started to undertake relief and reconstruction efforts in parts of Iraq, they have come under criticism from international relief organizations and others for not doing enough to quell looting and other civil disorder. U.S. commanders have insisted on the need to focus first on completing their combat missions.

"We believe we're fulfilling our responsibilities within the conditions and the parameters that we're currently operating under," Army Brig. Gen. Vincent K. Brooks, deputy director of operations for the U.S. Central Command, told a news conference in Qatar yesterday. "As I continue to emphasize, the work of combat operations has not completed itself yet. We're still working on eliminating any remains of the regime."

Brooks said the U.S. military command opposed taking blanket action throughout Iraq, such as imposing a nighttime curfew. He said how U.S. troops ensure neighborhood security is being left largely to the discretion of individual commanders.

A senior military intelligence officer said U.S. officials were uncertain about just how hard to crack down -- whether, in his words, it would "improve our support from the population" if the looting were allowed "to run its course" or U.S. forces were ordered to start shooting looters. "No one really knows," the officer said.

At the same time, the officer added, reestablishing order -- and doing so sooner rather than later -- will be critical for long-term U.S. objectives in Iraq and in the Middle East.

"It will only take a small number of armed individuals or units to make our lives miserable, and lead to incidents that will result in civilian casualties that will adversely affect Arab public opinion and our strategic interests elsewhere in the region," the officer said. "Even with [Saddam] Hussein gone, there are plenty of people in Iraq who will oppose us on nationalistic and religious grounds. It may take them awhile to get organized, and we must do everything we can to keep them from doing so."

Central to U.S. plans for stabilizing the country is jump-starting a political debate among Iraqis about the shape of a new government. To this end, a senior Pentagon official released new details yesterday about a meeting planned in Nasiriyah for Tuesday, the first of what U.S. authorities envision as a series of town hall-style discussions to define issues and identify prospective Iraqi leaders.

About 100 people have received invitations to attend from Franks, the official said. One third of those invited are from Kurdish-occupied northern Iraq or outside the country, the rest from inside.

The meeting is being hosted by Jay M. Garner, the retired three-star U.S. Army general who is heading a provisional authority with relief and reconstruction responsibilities. And a "hosting committee" has been established with three Americans representing the Pentagon, State Department and White House, and three others representing Britain, Australia and Poland.

In Baghdad, Marines prepare to ford river to building in background to prevent it from being used as a sniper site. Security needs in Iraq require the military to continue its troop buildup.