Updated

An offer by Portugal to take in detainees released from Guantanamo Bay will bring the U.S. closer to its goal of closing the offshore military prison, an American diplomat said Thursday.

Clint Williamson, U.S. ambassador-at-large for war-crimes issues, said the gesture marks a breakthrough in efforts to find new homes for detainees who would risk persecution or torture in their native countries.

"We certainly welcome this initiative," Williamson said in an interview with The Associated Press. "We have approached over 70 countries at this point, and I personally visited a number of those capitals, raising this with other governments."

As many as 50 of the roughly 250 inmates remaining at the U.S. Navy base in southeast Cuba would risk mistreatment if sent back to countries such as China, Algeria and Syria, according to human rights groups. The U.S. has described a lack of resettlement options for them as an obstacle to emptying the prison.

Portugal's offer was included in a letter that Portuguese Foreign Minister Luis Amado sent to his European Union counterparts.

The EU "should send a clear signal of our willingness to help the U.S. government resolve this problem, namely by taking in the detainees," the letter said.

Thus far, Albania is the only country that has accepted Guantanamo detainees on humanitarian grounds, taking in five members of China's Uighur ethnic minority in 2006.

Human rights groups also urged European countries to follow Portugal's lead and help the U.S. close the detention center, as President-elect Barack Obama has pledged to do soon after taking office on Jan. 20.

"At the change of administration, we hope there will be a number of countries that come forward and realize this is a critical opportunity to turn the page on Guantanamo," said Emi MacLean, an attorney with the New York-based Center for Constitutional Rights.

The U.N.'s torture investigator, Manfred Nowak, recommended last month that European countries take in Guantanamo inmates who cannot be sent home.

Williamson said his office is involved in discussions with several EU countries, but governments have been reluctant to accept men from Guantanamo because of security and political concerns.

"In some cases, they have just been reluctant to associate themselves with an unpopular policy related to Guantanamo," Williamson said.

A Thursday statement by Human Rights Watch said diplomatic efforts have stalled in part because the U.S. has been unwilling to resettle detainees within its own borders.

A federal judge in October ordered the government to allow a group of 17 Uighurs who have long been cleared for release from Guantanamo to live in the U.S. But the transfer has been held up by appeals.

The administration has said it is continuing efforts to find another country to accept the Uighurs, since the detainees might be tortured if they are turned over to China. Beijing has long said that insurgents are leading an Islamic separatist movement in a remote western region.

One of the attorneys for the Chinese Muslims, Seema Saifee, said Portugal's offer was "more than I heard before" but she was skeptical the men would be freed anytime soon.

"I'll believe it when I see it," she said.

Williamson said the U.S. has discussed the Uighurs' case with Portugal and other European governments but declined to provide additional details.