The US says it has arrested one of al-Qaeda's highest-ranking operatives, as he was on his way home to Iraq to plan future attacks.
Abd al-Hadi al-Iraqi has been taken to Guantanamo Bay
The Pentagon said Abd al-Hadi al-Iraqi was now in Guantanamo Bay.
He had been going to Iraq to take over al-Qaeda operations and possibly plot attacks on Western interests, it said.
He was accused of commanding attacks on coalition forces in Afghanistan, and of involvement in plots to assassinate Pakistani President Pervez Musharraf.
Pakistani Interior Minister Aftab Khan Sherpao described the arrest as a "welcome development".
An Afghan defence ministry spokesman said it was "a major success" that would "help to get to the high-ranking terrorist network figures and... have a deeply negative effect on the network".
According to information about him provided by the Pentagon, Mr Hadi was a key paramilitary commander in Afghanistan during the late 1990s, before taking charge of cross-border attacks against US and coalition troops from 2002 to 2004.
A US intelligence source told the BBC he was arrested late last year in an operation which involved the CIA.
It was not clear where he was detained, or where he has been held since.
A spokesman confirmed that Mr Hadi had arrived at Guantanamo Bay, and was being processed.
"Administratively and medically we're reviewing the information about him. He goes through a medical review... he's being put into our facility and treated like the rest of the detainees," Cmdr Rick Haupt told BBC News from Guantanamo Bay.
He said the Red Cross would be permitted to visit Mr Hadi.
He "will be treated appropriately... in accordance with US law and international obligations", the Pentagon said.
Mr Hadi would undergo a combatant status review to determine whether he should face a military tribunal, it said.
He is being treated as a "high-value detainee". There are 14 other such detainees among nearly 400 prisoners at Guantanamo Bay.
BBC security correspondent Gordon Corera says Abd al-Hadi al-Iraqi is one of al-Qaeda's most senior operational commanders.
According to the Pentagon information, he served in Saddam Hussein's Iraqi army, reaching the rank of major before crossing into Afghanistan to join al-Qaeda.
Born in Mosul, Iraq, apparently in 1961, he allegedly rose to a position of power and responsibility within al-Qaeda.
He is described by the US state department as one of Osama Bin Laden's "top global deputies", personally chosen by the al-Qaeda leader to monitor operations in Iraq.
A state department website advertised a reward of up to $1m (£500,000) for the capture of its quarry, who was described as 5ft 11in (180cm) tall, with a pale complexion, "a moustache and a long, heavy beard that is starting to grey".
"He has a reputation for being a skilled, intelligent, and experienced commander and is an extremely well-respected al-Qaeda leader," it said.
Pentagon spokesman Bryan Whitman said the suspect was "one of al-Qaeda's highest-ranking and senior operatives at the time of his detention.
"He is associated with leaders of extremist groups allied with al-Qaeda in Afghanistan and Pakistan, and including the Taleban," he added.