The others are Moazzam Begg, 36, a teacher from Birmingham, England, who was arrested in Pakistan in January 2002, and London residents Richard Belmar, 25, arrested somewhere in Pakistan, and Martin Mubanga, 31.
According to U.S. authorities, Mubanga, who was captured while visiting family in Zambia in 2002, was a terrorist-in-training who fled Afghanistan during the war and had a list of more than 30 Jewish targets in New York he was studying for attack.
_____U.S. to Release Prisoners_____
Video: Five Guantanamo Bay prisoners will be released within weeks by the United States.
All five detainees have alleged mistreatment in custody. Abbasi and Mubanga have said they were repeatedly abused during interrogations at Guantanamo through use of frigid and stifling temperatures, short shackles and random beatings.
The U.S. government "must know that it's hemorrhaging world credibility," said Barbara Olshansky of the Center for Constitutional Rights, who represents several dozen detainees. Releasing the detainees "is a way to stanch the bleeding," she said.
Some attorneys for detainees say they believe the administration is hoping to avoid having to defend in court its alleged practice of sending suspects to foreign prisons where questionable interrogation tactics are used. "The political folks have decided this is now hurting the administration and they need to make it go away," said Brent Mickum, an attorney for Mubanga. "And they're looking to avoid having any bad precedent that would affect their ability" to transfer detainees to third countries.
Blair, who is the Bush administration's most staunch foreign ally, has continually defended the detention of the British men, even while negotiating for their freedom. But other members of Blair's government, including Straw and Attorney General Peter Goldsmith, have publicly declared that the military tribunals the Bush administration established for the detainees did not meet international standards of fairness.
On Tuesday, the British government portrayed the planned releases as a political triumph for Blair, who is often criticized for having extracted few tangible benefits from Bush, a highly unpopular figure in Britain. "Had it not been for our alliance" with the United States, Straw told the House of Commons, the men would not be going free.
Menzies Campbell, foreign affairs spokesman for the Liberal Democrats, the third-largest party in Parliament, told lawmakers that "the detention of these men violated all legal principle. Their civil rights were systematically and deliberately abused and they were denied due process."
Geraint Davies, a member of Blair's Labor Party who represents the parliamentary district where Abbasi lives, welcomed his constituent's release. "Clearly he's not a person beyond suspicion," Davies said. "But if he's done anything wrong, he should be charged in a court of law. It's important that if Britain is to stand shoulder to shoulder with America to fight for peace and democracy, we can't have Guantanamo Bay stand as an example of injustice and double standards."
Frankel reported from London. Staff writer Dana Priest contributed to this report.