WASHINGTON - Attorney General Eric H. Holder Jr. said yesterday that there may be 50 or more trials of Guantanamo Bay detainees as the Obama administration works to shut the detention center by early next year.

Holder discussed the plan before the Senate Judiciary Committee, where the senior Republican, Alabama Sen. Jeff Sessions, called him "too silent" on terrorism. A second GOP lawmaker, South Carolina Sen. Lindsey Graham, said Holder was "on the right track" in handling detainees.

Sessions criticized Holder for the release of Bush administration memos that authorized harsh interrogation techniques. Sessions said the memos gave important information to America's enemies.

Holder said protecting Americans from terrorists was his top priority.

Under questioning from Graham, Holder outlined efforts to close the detention center in Cuba. Last week, the administration shipped 10 detainees from Guantanamo, leaving 229 there. President Obama has ordered the center closed by January.

Graham said he expected about one-quarter or fewer of the inmates to be brought to civilian or military trial. Holder said he thought that figure was "about right."

Holder did not commit to any specific figure and said authorities had worked through only about half the detainee cases so far. "I don't think we're going to have a very huge number" going to trial, Holder said.

If the 25 percent figure were to hold, it would mean about 56 detainees would face a trial of some kind by U.S. authorities. A separate group of detainees would be sent to foreign countries.

A third group, the most difficult, would not be released or put on trial. Holder said officials were discussing how to handle such suspects and whether new legislation would be required to hold them. Even without a trial, he said, a judge would have to review the basis for holding such detainees.

Graham agreed. "I think you're on the right track," the senator said. "I want an independent judiciary basically validating what the intelligence community and the military says about this person."

Also yesterday, Spain's foreign minister, Miguel Angel Moratinos, said the United States had asked his country to accept four Guantanamo detainees. He said Spain would respond when it had studied the detainees' circumstances and the legal consequences of taking them in.

Last week, the Obama administration sent four Chinese Uighurs - Turkic Muslims from China's far western Xinjiang region - from Guantanamo to Bermuda. The Pacific island nation of Palau agreed to take in 13 other Uighurs still being held.

But the Uighurs appear reluctant to temporarily resettle in Palau, said Joshua Koshiba, a Palauan official who leads a committee on U.S.-Palau relations.

Last weekend, Palau sent a fact-finding team to Guantanamo to meet with the 13. Koshiba has been in contact with the team since their trip.

Possibly only one Uighur wants to move to Palau, he said, without providing details of the discussions.

Sending the Uighurs back to China was not an option because of U.S. concerns that Chinese authorities, who consider them separatists, would immediately arrest the men.