The Bush administration could announce plans by the end of its term in January to close Guantanamo prison and an upcoming Supreme Court ruling might be the impetus for this, senior U.S. officials and experts say.

The government is under international and domestic pressure to close the prison, which opened at the U.S. naval base at Guantanamo Bay on Cuba in January 2002 to house terrorism suspects caught after the invasion of Afghanistan.

"A decision could be made in this administration to announce the closure of Guantanamo. It is unlikely in the next nine months that Guantanamo could be physically (closed) but it is possible the policy decision could be taken to close it," said a senior U.S. official, who spoke on condition he was not identified because of the sensitivity of the issue.

Officials say planning and debate has intensified in recent months over how to deal with Guantanamo, which President George W. Bush acknowledges has tarnished America's image and human rights advocates say has damaged U.S credibility.

"Everyone is agreed that we need to find a way that eventually leads to the closure of Guantanamo, which is the president's policy decision. It is a very complicated matter," said National Security Council spokesman Gordon Johndroe.

The Supreme Court is expected to rule within weeks whether Guantanamo prisoners have rights under the U.S. Constitution even though they are held on the base in Cuba, where the United States has had a presence for about 100 years.

The court decision could influence whether the U.S. government announces plans to close the prison before Bush leaves office in January 2009, several officials said.

"If the Supreme Court concludes that the detainees have constitutional rights, then there would be little legal difference between holding them in Guantanamo or holding them on the (U.S.) mainland," one senior official said.

"It's possible the Supreme Court decision could provide an impetus to a policy decision to close Guantanamo," he added.

"Legal black hole"

Most of the 280 prisoners at Guantanamo have been confined for years without charges. About 500 prisoners have been released, and the United States has said it intends to try 60 to 80 of those still in detention under war crimes tribunals.

Matthew Waxman, a former senior Defense and State Department official who dealt with detainee policy, has argued strongly for the closure of Guantanamo but he said the Supreme Court's decision could "cut both ways."

If inmates were now seen to have the same rights in Guantanamo Bay as on the U.S. mainland, then there could be little strategic reason to move them.

"The major criticism of Guantanamo is that it represents a so-called legal black hole," said Waxman, now a professor at Columbia Law School in New York.

Bush and other senior U.S. officials, including Defense Secretary Robert Gates and Secretary of State Condoleezza Rice, have all said they want Guantanamo Bay closed but they point to logistical and other problems.

There is also a drive to announce the closure before Bush leaves office rather than have his successor claim credit.

All of the presidential candidates have expressed a wish for Guantanamo to be closed and while the policy decision could be taken by this administration it will be up to them to implement it.

White House, Defense, Justice and State Department lawyers are still arguing the options, including the transfer of detainees to high security military prisons in the United States, moves that will be opposed by local politicians.

The Justice Department is concerned that transferring the detainees to the United States would result in an onslaught of litigation from detainees who would try to use the U.S. justice system to seek their release.

One option is the Disciplinary Barracks at Ft Leavenworth Army base in Kansas, but the state's senior Republican senator, Sam Brownback, has made clear he will fight that. A naval facility in South Carolina is also being considered.

Senior U.S. officials also hope countries reluctant so far to take home their own detainees will step forward once the U.S. government makes clear its intention to close the prison.

"Our allies talk a lot about concern of Guantanamo Bay but when they are asked to take their foreign nationals back, then they tend to stop talking," said Johndroe.