The Bush administration should demonstrate America's long-term commitment to Iraq by announcing a multiyear, multibillion dollar reconstruction program, a panel of prominent scholars, former officials and business leaders said in a report released Wednesday.

The task force's recommendations come as congressional Democrats stepped up pressure on the Bush administration Tuesday to provide estimates for rebuilding Iraq -- something analysts say could cost tens of billions of dollars.

Senate Democratic Leader Tom Daschle, said Democrats would introduce a measure this week calling for no additional tax cuts or additional spending until the costs of the war are known.

"How in the world can we agree to a budget if we're going to be off by hundreds of billions of dollars because of the war," Daschle told reporters.

The Pentagon has said any estimates offered now would be meaningless because of uncertainties about how long the war would last, how fierce resistance would be, what international support would be available.

Pentagon officials have begun offering details of their vision of a post-Saddam Iraq. On Tuesday, Pentagon officials said the United States would put Iraqi soldiers to work rebuilding the country and pay to keep Iraq's civilian government bureaucracy running. They would hope to turn over control to an interim Iraqi government within months.

In its report, the Independent Task Force on Post-Conflict Iraq said U.S. goals should include eliminating weapons of mass destruction, ending Iraqi contacts with terrorist organizations, ensuring the country's territorial integrity and building democratic institutions.

"In Iraq -- where U.S. efforts will inevitably involve uncertainty, trial and error, and uneven progress -- U.S. success will depend on America's determination to stay the course," it said.

The panel, sponsored by the Council on Foreign Relations, was headed by James Schlesinger, who held Cabinet positions in the Nixon, Ford and Carter administrations, and Thomas Pickering, a former top State Department official.

It estimated that the United States could have to spend $20 billion a year for several years for a postwar force. It would need an additional $2.5 billion for reconstruction and $500 million for humanitarian aid. Aid groups say the United States has provided less than $1 million in humanitarian aid so far.

The panel also said the United States should deploy forces to provide security and humanitarian aid, work closely with other nations and international organizations in rebuilding Iraq, and ensure that Iraqis play key roles in the administration of public institutions.

While Iraqis should control the country's oil, U.S. officials should try to ensure that oil revenues benefit the people of Iraq, it said.

A Pentagon official, speaking on condition he not be identified, said the United States expects the oil industry would continue to be overseen by the officials of the United Nations who now run the oil-for-food program under the U.N. sanctions regime.

At a Senate Foreign Relations Committee hearing Tuesday, the director of the Security Policy Studies Program at George Washington University, said assistance from other nations will be essential given the enormous postwar costs.

He said an occupying force could cost $12 billion to $48 billion in the first year alone, with another $3.5 billion in humanitarian assistance needed in the first year.

In addition, $30 billion to $100 billion could be needed in the next five to 10 years for rebuilding Iraq, plus $12 billion over five years for establishing an Iraqi government.

"The numbers I have offered you are beyond our capacity to do all alone," he said.

Defense Secretary Donald H. Rumsfeld said the money to administer Iraq after a war could come not only from the United States but also from seized Iraqi assets, the oil-for-food sanctions program and donations from other countries.

"It's not as if the country is destitute," Rumsfeld said.