Human rights activists hold a banner with a picture of Shaker Aamer, a detainee at Guantanamo Bay, during a rally near the White House in 2013. (Manuel Balce Ceneta/AP)

The Obama administration has notified Congress of its intent to send Shaker Aamer, a suspected al-Qaeda plotter held at Guantanamo Bay, Cuba, for more than 13 years, back to Britain, yielding to a lengthy campaign to secure the British resident’s release, officials said Friday.

President Obama discussed the decision to move Aamer, whose case has become a cause celebre among rights groups in Britain, with Prime Minister David Cameron in a phone call Thursday.

Aamer, who was captured in Afghanistan in 2001 and brought to Guantanamo Bay in February 2002, was a “close associate of Osama bin Laden” who fought in the battle of Tora Bora, according to U.S. military files disclosed by the anti-secrecy group WikiLeaks.

A Saudi national who married a Briton in the 1990s, Aamer has been the focus of high-level discussions between the two countries, as British officials have increased pressure on the Obama administration to put aside lingering concerns about the risks associated with releasing Aamer and set him free. He has never been charged with a crime.

This year, British lawmakers visited Washington to lobby for the prisoner’s release, and Cameron raised the issue in talks with Obama.

Guantanamo Bay detainee Shaker Aamer was allegedly a “close associate” of Osama bin Laden. (Department of Defense)

Aamer is the last of several British residents or citizens held at Guantanamo starting in 2002.

Born in Medina, Saudi Arabia, in 1966, Aamer attended college in Jeddah and trained to be a nurse at a military hospital. He lived briefly in Atlanta in 1989 before moving to Gaithersburg, Md. After the Persian Gulf War began in 1990, he got a job as a translator for the U.S. military in Saudi Arabia, according to the military files.

While the Obama administration cleared him for release in 2010, military officials have expressed concern about the possibility that Aamer, who has been an influential figure among other prisoners at Guantanamo Bay, could return to militant activity once released.

Ramzi Kassem, a law professor at the City University of New York, who along with students at his legal clinic represents Aamer, said the decision was years overdue.

“This should have happened long ago, but today being the most important holiday in the Muslim calendar, I can’t think of a better present for Shaker and his long-suffering wife and children in London,” he said.

A senior U.S. defense official, speaking on the condition of anonymity to discuss internal decision-making, said Defense Secretary Ashton B. Carter approved the transfer “following a thorough review of his case and taking into consideration the robust security assurances that will be provided by the British government, one of our strongest allies, who has supported our efforts to close the detention facilities at Guantanamo Bay.”

A British government spokesman said the Obama administration had informed British officials of the decision. “As the U.S. has said, we have one of the most robust and effective systems in the world to deal with suspected terrorists and those suspected of engaging in terrorist-related activity,” the spokesman said.

Aamer has denied any involvement in terrorism.

The decision comes as the White House prepares for a showdown with Congress over Obama’s desire to close the facility before he leaves office in 2017. Officials are racing to finalize a plan that would move some prisoners to the United States, while the rest would be repatriated or transferred to third countries.

But many lawmakers in both parties have long opposed bringing any detainees to the United States for trial or continued detention. The administration must notify Congress 30 days before moving any prisoners out of the military detention facility.

Rep. Mac Thornberry, chairman of the House Armed Services Committee, said he had “grave concerns” about releasing inmates who might take up arms again.

“Shaker Aamer certainly fits that bill if he is released to the U.K. because I do not believe that the British Government has the ability to hold or try him,” Thornberry (R-Tex.) said in a statement. “Despite the rhetoric of a sophisticated PR campaign, it is clear to me that this is a dangerous individual whose release will put Americans at greater risk.”

A total of 114 detainees remain at the prison; 52 are cleared for release. Carter has also approved the transfer of a Mauritanian prisoner, the 10th detainee since he took over in February.

Although British officials have said Aamer won’t be arrested upon his return, he is certain to remain on the radar of security services there. Another British former Guantanamo detainee, Moazzam Begg, was arrested and held for seven months last year in a maximum-security prison before being released after a terrorism-related case against him collapsed.

Britain’s main domestic intelligence agency, MI5, keeps tabs on several thousand people with suspected ties to extremist causes. But it only has the resources and the legal mandate to actively monitor a relatively small proportion of them at any given time.

At Guantanamo Bay, Shaker and another Saudi inmate, Ghassan al-Sharbi, have long been considered leaders of the prisoner population. Aamer’s alleged relationship with Bin Laden gave him “immediate stature in the camp,” said Mike Bumgarner, who was in charge of the detention facility between April 2005 and July 2006.

Though Aamer was known by military guards as the “professor,” the leaked assessments said he was an “extremely egotistical” individual who sought to manipulate others.

“He had his hands on all levers of power down there,” Bumgarner said.

Bumgarner also said Aamer worked at times to “bring down the temperature at the camp,” create a safer environment for guards and end hunger strikes.

Julie Tate in Washington and Griff Witte and Karla Adams in London contributed to this report.

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