President Bush grabbed headlines with his pledge to tear down Iraq's notorious Abu Ghraib prison, but Monday night's promise left the White House scrambling on Tuesday to persuade Congress to endorse something it specifically rejected last year.

Last fall, Bush requested $400 million to build two maximum-security prisons in Iraq, but Congress reduced the request to $100 million, about the cost of one medium-security facility in the United States. In April, the U.S.-led occupation authority informed Congress it would build a single 4,400-bed prison near Nasiriyah, south of Baghdad.

White House spokeswoman Claire Buchan said U.S. taxpayers will finance a second prison to replace Abu Ghraib. She said there is sufficient flexibility within the $18.4 billion in Iraq reconstruction aid approved in October to build the prison.

But Tim Rieser, a Democratic aide on the Senate Appropriations foreign operations subcommittee, which is monitoring the reconstruction, said Bush would have to consult Congress on such a large transfer of money. "For all intents and purposes, the money is not there," Rieser said.

It is clear that Bush's dramatic promise to raze Abu Ghraib will take quite some time to fulfill. The prison -- notorious for torture and killing during Saddam Hussein's reign and a still-growing prisoner abuse scandal under U.S. control -- will not be torn down until its replacement is ready, Bush said. And aides in Congress and the occupation authority said construction of a bare-bones facility would take 18 months to two years.

If the White House intends the new prison to be "a showcase for progressive Western penal thinking," it may take longer to build health, athletic and rehabilitation facilities along with the cellblocks, a House Republican aide said.

The prison in Nasiriyah is already behind schedule, occupation documents indicate. In January, occupation authorities said they would direct $33 million to the project. By April, nothing had been spent. The occupation authority cited only one accomplishment in its latest report to Congress: approval of "the initial scope of work for the new prison."

The report said the Defense Department expects to break ground on the prison in June, but occupation officials said yesterday in Baghdad that they had no indication that would happen.

That slow pace has some advantages. Of the $18.4 billion in reconstruction funds that Congress approved in October, a little more than $4 billion has been obligated to specific projects, David Nash, a retired admiral managing the spending of U.S. tax dollars, said at a Pentagon briefing Monday. That leaves plenty of unspent money available for a second prison.

But unless the White House breaks its pledge not to ask for more reconstruction money, the additional prison construction funds will have to come from other projects -- a potential public relations problem. Members of Congress have already questioned the administration's shift of $213 million from drinking water and democracy-building projects to administrative expenses and U.S. Embassy operations. A shift of $100 million or more for prison construction would likely need congressional approval.

The pledge was not greeted with universal applause. Mahmoud Othman, a Kurd on the U.S.-installed Iraqi Governing Council, told an Australian newspaper that he wanted the prison to be turned into a museum, preserving the memories of the crimes that took place there.

Interim interior minister Samir Shakir Mahmoud Sumaidy and the human rights group Amnesty International also objected to its demolition. "While I can understand the wish to abolish Abu Ghraib, to remove the memory and the stain on the reputation of those who perpetrated the criminal acts against its prisoners, I personally don't think a building itself has a meaning, positive or negative," Sumaidy told the Australian newspaper.

Amnesty International spokesman Alistair Hodgett said the demolition could interfere with war crimes and human rights prosecutions. "We believe it's ultimately up to the Iraqis to decide the fate of the prison," he said.