Those mistakes, which ranged from initially having too few people on board to handle the workload to misreading Congress, could push the prison's closure well beyond the January deadline, which Obama announced with great fanfare two days after he took office.

The administration is expected to announce within days the results of its review of legal cases against the remaining detainees at Guantanamo, a review that originally was scheduled to be finished in July. Among its conclusions, the administration is expected to say whether it will prosecute the accused mastermind of the Sept. 11, 2001, terrorist attacks and four alleged coconspirators in a federal civilian court.

"We hope we'll see the announcement very soon on the 9/11 case, that they're going to prosecute Khalid Shaikh Mohammed and the other conspirators in federal court," said Ken Gude, a scholar at the Center for American Progress and author of the report. The liberal policy organization has close relations with the Obama administration, which declined comment on the report.

Gude said the White House made mistakes in implementing Guantanamo policy from the very beginning. Two task forces - one set up to study the case files of the more than 200 detainees held at the prison and the other charged with examining the overall detention policy - fell behind almost from the start.

A key problem was that the Obama team was only hours old and didn't have enough people to follow through quickly after the president announced the closing plan.

Gude said the administration also made a critical mistake by not moving quickly to move some detainees out of Guantanamo. For example, he said, the administration should have worked with the Virginia congressional delegation to smooth the way politically to release a group of Uighurs to northern Virginia, where there is a community of the Chinese Muslims.

"They could have put that together in six to eight weeks," he said.

With little groundwork done to move some Guantanamo detainees to the United States or elsewhere, the administration made what Gude called its "biggest mistake" in April by asking Congress for $80 million to finance the prison closure.

Asking Congress for money for Guantanamo opened the door for conservatives on Capitol Hill, and the Obama administration was caught off guard when they began aggressively pushing back against the funding, Gude said in his report.

He called the backlash "ridiculous" because it was based on the implied argument that the country's maximum-security prisons could not hold terrorists transferred from Guantanamo and that the closing of the prison would thus endanger Americans.

Nonetheless, Gude said, "The White House failed to support its allies in Congress that were willing to push back against the fear-mongering. . . . The result was Congress overwhelmingly voting to bar the release of any Guantanamo detainees into the United States and placing severe restrictions on any other kinds of transfers."

That also made it harder for the United States to persuade other countries to take some of the detainees for release or detention. Gude noted that 16 countries had agreed to accept some detainees.

Gude and the Center for American Progress, headed by former Obama transition chief John Podesta, urged several steps to get the prison closing on track. They include:

Setting a new deadline of July, rather than letting the January deadline slip.

Prosecuting the alleged Sept. 11 conspirators in federal court and limiting military commissions to what they called battlefield crimes.

Limiting military detention to those captured in combat zones and using criminal law to try those captured "far away" from any battlefield.

Sending those convicted in federal courts to maximum-security prisons in the United States, and sending those in military custody to the prison at Bagram Air Base in Afghanistan.