Al-Zubaydi, a former member of the Iraqi Revolutionary Command Council and central Euphrates regional commander, was no. 18 on a list of the 55 most-wanted figures from Saddam Hussein's regime.
Meanwhile, the retired Army general in charge of an interim administration in postwar Iraq told patients and doctors Monday at a Baghdad hospital that American help was coming, but could take some time.
Lt. Gen. Jay Garner visited Baghdad's 1,000-bed Yarmuk hospital, which was overwhelmed with Iraqi casualties in the final days of the war. Its wards, including the coronary and respiratory care units, were then stripped of almost everything by looters.
"We will help you, but it is going to take time," Garner told doctors.
Some were unimpressed.
"If they give us anything, it is not from their own pockets. It is from our oil," said a female doctor, Iman. "Saddam Hussein was an unjust ruler, but maybe one day we could have got rid of him and not had these foreigners come into our country."
Earlier, as his plane touched down, black clouds of smoke still drifted through Baghdad's skies from fires set by looters in a lawless city.
In other developments:
Al-Zubaydi, a former prime minister and deputy prime minister, was one of the key figures in suppressing the Shiite uprising that followed Iraq's defeat in the 1991 Gulf War.
He was featured in Iraqi news film kicking and beating captured Shiite rebels.
With Monday's capture, eight of the 54 wanted members of Saddam's inner circle are now in custody, though none of them is from the very top of the list. A ninth figure, Ali Hassan al-Majid, a top adviser to Saddam, is believed to have been killed in an airstrike in Basra.
Saddam Hussein's son-in-law, Jamal Mustafa Abdallah Sultan al-Tikriti, and one of the toppled Iraqi leader's bodyguards surrendered to an Iraqi opposition group, the group said Sunday.
Other top arrests by coalition forces include Watban and Barzan Ibrahim Hasan al-Tikriti, two of Saddam's three half brothers; Hikmat Mizban Ibrahim al-Azzawi, the finance minister and deputy prime minister; science adviser Lt. Gen. Amer al-Saadi; and Samir Abd al-Aziz al-Najim, a senior figure in Saddam's Baath Party.
In Baghdad, Garner, who will report to Central Command chief Gen. Tommy Franks, said he intended to complete his work and leave as soon as possible, but declined to give a timeframe.
The ORHA is to coordinate delivery of outside assistance to the 24 million Iraqis; oversee rebuilding of the nation's infrastructure, in disrepair after a decade of U.N. sanctions, neglect by Saddam's regime and three weeks of U.S. bombing; and oversee the establishment of an interim Iraqi government.
For ordinary Iraqis, however, the first needs are for water and electricity — knocked out during the war — and, especially, for security in a city wracked by almost two weeks of looting.
At the city's major electrical plant, Maj. Andy Backus of the U.S. Army Corps of Engineers told Garner workers had managed to restore power to only 1 percent of the city, but "hopefully, this evening we will have the lights on in 10 percent of Baghdad."
Electrical power is key to the proper functioning of other important civilian utilities, like water and sanitation.
The Americans' most difficult challenge undoubtedly will lie in trying to forge a peaceful, cooperative structure among Iraq's political, religious and ethnic factions.
Shiite leaders — who are strongly opposed to the U.S. military presence, though pleased to see Saddam go — have called for political demonstrations during upcoming holy days, which run from Tuesday to Thursday.
No Iraqi figures have spoken out in support of a strong U.S. role in the coming months.
Even Chalabi has described Garner's job as one of getting Iraq's infrastructure and services back in shape "in a few weeks," after which Iraqis would take over and the Americans would be limited to military roles.