Pakistani authorities said Mohammed, branded by Washington as one of al Qaeda leader Osama bin Laden's "most senior and significant lieutenants," would be extradited to the United States. But a US official said Mohammed was expected to be handed to US authorities and interrogated in an undisclosed foreign country.

The White House said Mohammed, one of three al Qaeda suspects to be detained in an early morning swoop in the Pakistani city of Rawalpindi, was "a key al Qaeda planner and the mastermind of the September 11 attacks."

"The United States commends Pakistani and US authorities on the completion of a successful joint operation, which resulted in the detention of several al Qaeda operatives," White House spokesman Ari Fleischer said in a statement.

Analysts describe Mohammed as a pivotal figure in the al Qaeda network who vetted all its recruits and who may know the whereabouts of both bin Laden and Mullah Mohammed Omar, fugitive leader of Afghanistan's former Taliban government.

"It was the work of Pakistani intelligence agencies... It is a big achievement. He is the kingpin of al Qaeda," said Rashid Qureshi, spokesman for Pakistani President Pervez Musharraf.

President Bush views Pakistan as a key supporter in the war on terror he declared after blaming al Qaeda for the September 11 suicide plane attacks on New York and Washington.

Pakistani Swoop

Pakistani Information Minister Sheikh Rasheed Ahmad said Mohammed, believed to be in his late 30s, would be handed over to the United States.

"Right now, I can't say whether Mohammed will be moved tomorrow or next week. It could be next week, it could be tomorrow," he said.

Mohammed was one of three al Qaeda suspects detained in a raid on a house in Rawalpindi, a teeming city near the Pakistani capital Islamabad.

Officials said the suspects were a Pakistani and two foreign nationals of Arab origin.

In June 2002, US investigators identified Mohammed as the probable mastermind behind the September 11, 2001, attacks.

He was indicted in the United States in 1996 for his alleged role in a plot to blow up 12 American civilian airliners over the Pacific.

Ahmed Rashid, author of an acclaimed book on the Taliban and its links to al Qaeda, described Mohammed as a brilliant organizer who knew everyone in bin Laden's operation.

"All the recruits in the past 11 years have passed through his hands," he said.

"He may well know about the whereabouts of Osama bin Laden and Mullah (Muhammed) Omar. He may know all the plans al Qaeda had after September 11," he said.

The Pakistani national held, Ahmed Qadoos, was arrested in Rawalpindi at about 3:30 a.m. on Saturday (5:30 p.m. EST on Friday) by armed security officials, who also took away a computer. "They shut family members in a room at gunpoint," his cousin Omar Khan said. "He is not linked with anything."

Ahmed has a wife and two children and lived with his parents. His father Qadoos is a retired microbiologist who had worked for the United Nations and has also lived abroad.

Mohammed was born in Kuwait, but his family is from Baluchistan, one of two Pakistani provinces bordering Afghanistan, according to a detailed profile published last year in the Los Angeles Times.

He is thought to be a relative of Ramzi Ahmed Yousef, now serving a life sentence for involvement in the 1993 bombing of New York's World Trade Center, later destroyed in the September 11 attacks.

Crackdown on Al Qaeda

Pakistani security agencies have been hunting al Qaeda members with the help of US intelligence agents since the ousting of the hardline Islamic Taliban government in neighboring Afghanistan in late 2001.

Hundreds of al Qaeda members and their Taliban allies are thought to have crossed into Pakistan since US-led forces began hunting for them in Afghanistan after the end of Taliban rule.

Pakistan says it has arrested more than 400 suspected Islamic militants since late 2001, but Mohammed is by far the biggest catch yet.

The United States put a US$25 million price tag on his head and the FBI posted him on its "most wanted" list of 22 individuals in October 2001.

"If bin Laden has been the architect of al Qaeda, Mohammed has been its engineer," the Los Angeles Times quoted US anti-terrorist investigators as saying last year.

Mohammed studied in the United States for a time, but ended up in Pakistan's northwestern city of Peshawar in the late 1980s where he and his brothers are said to have linked up with a small Arab circle that included bin Laden.

US investigators have been quoted as saying he traveled the globe as a key al Qaeda recruiter and coordinator.

He is suspected of involvement in the bombing of US embassies in Africa in 1998 and the attack on a US warship in Yemen in 2000.

After the events of September 11, 2001, Mohammed is thought to have moved between Afghanistan and Pakistan.

In September last year, Karachi police identified Mohammed as the man hit by a police sniper in a shootout with militants. This was later denied by a suspected Pakistani militant.

A Pakistani newspaper, reporting on the clash, said investigators believed Mohammed was the man who slit the throat of US reporter Daniel Pearl in front of a camera after the journalist disappeared in Karachi in January 2002 while investigating a story on Islamic extremists.

Pearl's dismembered body was found months later in a shallow grave on the outskirts of Karachi.

Other al Qaeda figures that Pakistan has arrested include Ahmed Omar Abdel Rahman, known as Binalshibh in the West, who was a key figure in the Hamburg cell suspected of carrying out the September 11 attacks. He is now in US custody.

(China Daily March 2, 2003)