Confronting cost estimates of at least $20 billion a year and fears that Iraq could become permanently dependent on a U.S. military presence, senior officials in the White House and Pentagon are questioning the Bush administration's most ambitious, long-term plans for Iraq's reconstruction.

These officials are leaning toward a quick exit from a country that U.S.-led forces conquered in less than a month. The administration remains committed to repairing and rebuilding war-damaged infrastructure, in many cases to standards considerably higher than before the war started, a senior defense official said. Indeed, San Francisco-based Bechtel Group was just awarded an initial $34.6 million contract to rebuild airports, water and electricity systems, roads and railroads.

But the far larger task of ensuring that Iraq emerges as a representative democracy friendly to U.S. interests and operating with a free-market economy would be left to an Iraqi interim authority, which could control key aspects of Iraqi governance within months.

"I don't think it has to be expensive, and I don't think it has to be lengthy," a senior administration official said of the postwar plan. "Americans do everything fairly quickly."

Concerns about the costs and duration of rebuilding Iraq are being raised by senior civilian planners at the Pentagon, as well as senior aides to President Bush. The president's budget director, Mitchell E. Daniels Jr., maintained in a recent report that Iraq "will not require sustained aid."

Even officials at the Office of Reconstruction and Humanitarian Aid, the umbrella group headed by retired Gen. Jay Garner that will lead the postwar effort, said they expect to measure their time in Iraq in "months, not years," though Garner suggested in an interview Saturday that the United States would persevere until democracy is established.

Such sentiments mark a departure from the lofty goals laid out within the administration and before the American public before the war began -- goals that a chorus of think tanks and former diplomats is imploring the administration to carry out. Still, the debate over what happens next is far from settled, with some powerful administration officials, especially in the Treasury and State departments, arguing for a longer-term commitment.

State Department blueprints sent to Congress before the war began laid out a vision for Iraq's reconstruction that would move the country aggressively toward "self-managed economic prosperity, with a market-based economy and privately owned enterprises that operate in an environment governed by the rule of law."

The electricity system would be rebuilt nearly to pre-1991 levels, before the long decline brought on by the Persian Gulf War, sanctions, neglect and government corruption. Within 180 days, clean drinking water would be available to 90 percent of the population, and trash collection would be available to 60 percent. Within 360 days, basic health care would be available to every Iraqi, and 6,000 schools would be rehabilitated and furnished with a new curriculum.

In six months, Iraqi ports would have six berths capable of unloading 25,000 tons of goods and equipment in 72 hours. By this time next year, new cellular phone hubs would be operational, and 80 percent of the agricultural sector would have reverted from state to private control.

Those documents followed Bush's own expansive vision, laid out Feb. 26 in a speech at the American Enterprise Institute, when he promised "a sustained commitment."

"America has made and kept this kind of commitment before in the peace that followed a world war," Bush said. "After defeating enemies, we did not leave behind occupying armies. We left constitutions and parliaments. We established an atmosphere of safety, in which responsible, reform-minded local leaders could build lasting institutions of freedom."

But the occupation of Germany lasted four years, and the occupation of Japan lasted seven. And the United States still maintains more than 110,000 troops in those two countries. Defense Department officials and some key White House officials now worry that the State Department's 360-day reconstruction goals would take far longer than a year and could sink the military into an open-ended deployment that would stretch on for years, if not decades.

So the debate continues over how many of those goals the United States can afford. Setting the bar low, a senior administration official said last week, "The president's goal is to leave Iraq on the road to prosperity and security and democracy -- or at least give them a fighting chance of it."

To succeed in transforming Iraq, government and private-sector cost estimates put the minimum drain on the Treasury at $20 billion a year for years to come, nearly $17 billion of that to support a peacekeeping force of 75,000 U.S. troops. Based on recent peacekeeping efforts in the Balkans, Yale University economist William D. Nordhaus has estimated the total postwar cost at $75 billion to $500 billion, and the duration of any successful occupation at a minimum of five years.

But defense and White House officials are shying away from historical models for the current task. In Japan, Germany, Bosnia and Kosovo, U.S. troops stayed so long that the money they spent and the security umbrella they provided became crutches for the local economies and governments, and the dependence was hard to break.

"The balance is getting out without walking away from our responsibility, but resisting what has happened in the past, when foreign forces come in and everyone wants them to stay forever," the defense official said.

One White House official said the preeminent reason to get U.S. military and civilian authorities out of Iraq quickly is to silence the increasingly vocal charge in the Arab world that the United States is a new colonial power.

"It's not because we're doing it on the cheap," the official said, "but because we don't want to have an overbearing presence there that can damage the longer-term view of the United States in the Arab street."

Such hedging is likely to exacerbate differences between the minimalist camp and some State Department officials, who still believe the United States should set its sights on spending whatever time it takes to create a true, pluralistic democracy with a thriving, entrepreneurial economy.

Andrew S. Natsios, administrator of the U.S. Agency for International Development, a part of the State Department, stressed that the real challenge in Iraq will be overcoming an Iraqi mind-set formed over decades of repression. And that could take years. "The biggest thing -- and it's going to take time to do it -- is to undo the palpable state of fear and terror," he said.

Treasury Department officials are also thinking big, hoping to encourage the adoption of a codified system of property rights and a rule of law for business operations, a transparent system of budgeting and taxation, the promotion of an entrepreneurial economy and, ultimately, the privatization of centrally planned state enterprises.

John B. Taylor, the undersecretary of the Treasury for international affairs, said the department hopes to create "a well-functioning market economy that is growing, creating jobs and is promising a future" for the Iraqi people. He said the course Treasury would like to set "most importantly undoes the changes of the last 25 years," recreating the conditions that existed before Saddam Hussein's central planning and three costly wars.

Taylor said that ambition does not conflict with the Pentagon's rapid timetable, because defense officials envision a phased withdrawal from Iraq. The functions that Treasury is leading may be among the last governance efforts transferred to the interim authority, he said.

Congress has approved $2.5 billion for reconstruction and relief, and that will last a year, White House budget officials say. USAID has awarded major contracts to rebuild Iraq's airports, water and electricity systems, roads, railroads and ports; to develop measurements of educational achievement, train teachers and revamp the educational system; and to promote participation in local governance.

But those contracts total just $49.3 million -- with an additional $645 million possibly available for infrastructure reconstruction over 18 months. That is a pittance compared with the $2.5 billion to $3 billion that experts say will be needed annually for several years.

"We know that the supplemental funds for Iraq are not going to carry the reconstruction effort very far into fiscal year 2004," which begins in October, Natsios told a House subcommittee April 9.

And that amount is dwarfed by the military spending that would be needed to maintain the peace, experts say. A study by the Council on Foreign Relations concluded that the United States would need to keep 75,000 troops in Iraq to maintain enough stability for reconstruction and the delivery of humanitarian assistance. That figure is the minimum proposed by the Congressional Budget Office, based on peacekeeping experiences in Bosnia and Kosovo.

"This is going to be a very tricky course that we are on," said James R. Schlesinger, a former defense secretary and co-author of the study. " . . . Many people who have the right vision about what should be accomplished do not, as of now, recognize how much of a commitment in time as well as money this is going to require."

Iraq experts warned that the administration could not count on Iraqi oil to foot the bill. James Dobbins, a former assistant secretary of state who directs the International Security and Defense Policy Center at Rand Corp., said Iraq's current production capacity of 2 million barrels of oil a day is enough to cover humanitarian relief under the United Nations' oil-for-food program and to pay war reparations to Kuwait and Iran that are not likely to be forgiven. Concerted foreign investment could raise production to 3.5 million barrels a day, Iraq's historic high, but that would take as long as five years, he said.

Pentagon and White House officials disagree with such warnings. One senior defense official questioned whether 75,000 troops would be needed even in the near future, saying the U.S. military force that deposed Hussein's government was not much larger. Some government functions could be turned over to an interim Iraqi government in a matter of months, the official said. Even the need for a new Iraqi military force could be obviated by moving U.S.-allied Kurdish fighters south toward Baghdad, the official suggested.

White House aides stress that Iraq is not a destitute country, like Afghanistan. Besides its oil reserves, the second-largest in the world, it has an extensive transportation, water, electricity and telecommunications infrastructure, an educated population and a recent history of entrepreneurship and relative affluence.

Pentagon officials take a very different tack, emphasizing that Iraqis have grown accustomed to intermittent electric power, unreliable and decrepit water and sewerage systems, and a terribly inefficient state-run economy.

From those disparate assessments, however, flow the same conclusion: Not much needs to be done to improve the average Iraqi's lot.

And that supports the goal of a quick exit. White House officials say their emphasis on speed is not because they fear the cost of a more extensive effort. The imperative, they say, is to avoid any perception in the broader Arab world that the war was about occupation.

"There's a sensitivity to the fact [that] you don't want a sustained American presence," one official said. "You don't want to Americanize Iraq, because that would interfere with foreign policy in the years ahead."

Rachel Bronson, director of Middle East studies at the Council on Foreign Relations, warned that short-term gains from a quick exit would be overrun by long-term costs if an unstable Iraq reemerges as a hostile regional power.

Dobbins noted that where the United States has committed troops and assistance over long periods -- Germany, Japan and Korea -- the efforts have been spectacularly successful. Where administrations have rushed out after military engagements, such as in Haiti and Somalia, the results have been dismal. Afghanistan, where the administration has resisted pressure to expand peacekeeping beyond the capital, is shaping up to be a failure as well, many experts say.

"We've done these things quickly, and we've done them well," Dobbins said, "but we've never done them quickly and well."

Staff writers David Hilzenrath in Washington and Monte Reel in Kuwait contributed to this report.

An Iraqi worker opens the tap of a gas pipeline yesterday at a power plant in Baghdad. Engineers hoped the plant would be operating by today.