Saifullah Paracha, the oldest prisoner at Guantanamo Bay, will be released after more than 16 years in custody, his lawyer has said.
The 73-year-old from Pakistan has been held on suspicion of ties to al-Qaeda but never charged with a crime.
In addition to being the oldest detainee, Mr Paracha has also been described as among the most unwell, with the New York Times reporting that he has heart disease, diabetes and high blood pressure.
Mr Paracha, who was captured in Thailand in 2003, was cleared by the prisoner review board along with two other men, according to Shelby Sullivan-Bennis, who represented him at his hearing in November.
He was "not a continuing threat" to the US, Ms Sullivan-Bennis said, adding that she believed he would be sent back to Pakistan in the coming months.
The US will have to negotiate a repatriation agreement with Pakistan, which could include restrictions such as not permitting him to leave the country for two years.
Mr Paracha once lived in the US and owned property in New York City.
Authorities alleged he was an al-Qaeda "facilitator" who helped two of the conspirators in the September 11 plot with a financial transaction. Mr Paracha claims he didn't know they were from al-Qaeda and denies any involvement in terrorism.
Mr Paracha is one of 40 prisoners still held at Guantanamo, down from a peak of nearly 700 in 2003.
The other two who were cleared for release are Abdul Rabbani, 54, also a Pakistani citizen, and Uthman Abdul al-Rahim Uthman, 40, from Yemen. Neither of the men have been charged with a crime.
Mr Uthman has been in Guantanamo since 2002 and is alleged to have been one of Osama Bin Laden’s bodyguards.
Mr Rabbani was captured in Karachi in 2002 and identified as an "enemy combatant". He says he was just a taxi driver and claims that he has been the victim of torture while in US detention.
The Pentagon was contacted for comment.