The United States wants to close the prison at Guantanamo Bay but needs assurances that detainees won't pose a security risk or face torture when they're sent to other countries, a senior U.S. State Department official said Monday.

"It really shows the conundrum that we're in," said John B. Bellinger III, the State Department's legal adviser. "We want to get out of the Guantanamo business while continuing to protect ourselves and protect others."

Bellinger said the U.S. wants to return many detainees but has been blocked by countries who don't want the men or who don't recognize them as nationals. Another obstacle has been getting assurances that detainees won't face human rights abuses upon their return or pose a threat to the United States.

"Many of these countries do not want their nationals back," Bellinger said. "It's difficult to even get to square one in terms of discussion with different countries if individuals can go back there."

President Bush has said he would like to close the prison, where some 450 men are held on suspicion of links to Al Qaeda and the Taliban.

Only 10 detainees have been charged with crimes and face military tribunals ordered by Bush, the first such trials since World War II. The Supreme Court could rule this week on the legality of the tribunals.

Senior European Union leaders pressed Bush during a recent EU-U.S. summit in Vienna to shut down Guantanamo and redouble efforts to make sure that human rights are not sacrificed in the war on terror.

Bellinger said he discussed the issue of closing Guantanamo with European officials at the Vienna summit. He said EU officials long opposed to the prison were beginning to see that closing it "is easier said than done."

Bellinger said the U.S. has begun talks with Britain about returning a group of British residents who have been held at the remote base on Cuba's southeastern tip.

A big headache for the U.S. has been what to do with a group of Uighurs, an ethnic group that lives mainly in western China. About two dozen Uighurs were captured by U.S. forces in Afghanistan.

China has demanded their return, but the United States feared they might face persecution there. China blames Uighur separatists for sporadic bombings and other violence in the Xinjiang region.

Five Uighurs were sent to Albania last month, but no other countries have offered to take in the rest.

Other nations "were concerned that the Chinese government would be very unhappy with them if they were to take the Uighurs," said Sam Whitten, head of the State Department's war crimes office.