U.S. officials hailed as a "big catch" Wednesday the arrest of a man accused of masterminding the bombing of the USS Cole and playing a leading role in the Sept. 11 terror attacks.

Pakistani authorities captured Waleed bin Attash (search), also known as Tawfiq Attash or just Khallad, who coordinated the activities of at least two of the hijackers who crashed into the Pentagon during the Sept. 11 attacks, U.S. counterterrorism officials said. He is also one of two figures described as plotting the bombing of the U.S. Navy destroyer on Oct. 12, 2000 in Yemen.

Khallad was arrested along with five other Al Qaeda suspects Tuesday during raids in the southern Pakistani city of Karachi. Pakistani and U.S. officials announced his capture Wednesday.

President Bush described Khallad as "one of the top Al Qaeda (search) operatives" -- saying he ranked just below Khalid Shaikh Mohammed, the captured No. 3 figure in the terror network.

Khallad is often described as one-legged but actually is missing his right foot.

"He's a killer," Bush said of Khallad. "He is one less person that people who love freedom have to worry about. ... It was a major, significant find."

U.S. counterterrorism officials described Khallad as among the top 10 Al Qaeda figures who remained at-large.

"This is a big catch," said Brig. Javed Iqbal Cheema, the head of Pakistan's counterterrorism unit. "I think he is very important."

American and Pakistani officials said Khallad, a Yemeni who also held Saudi citizenship, was active in plotting new terrorism. He will be interrogated by officials from both countries.

"With these arrests a major terrorist attack has been averted in Pakistan," said the country's interior minister, Saleh Faisal Hayyat.

In the Cole (search) attack, two homicide bombers rammed an explosives-laden boat into the Cole in the Yemeni port of Aden, ripping a gaping hole in the ship's hull and killing 17 sailors.

The other alleged Cole mastermind, Al Qaeda's Persian Gulf operations chief Abd al-Rahim al-Nashiri, was captured in November in the United Arab Emirates.

Two other alleged lower-ranking organizers of the attack recently escaped from a Yemeni prison. They were not believed to be among the six captured this week.

Khallad had also planned an attack on another Navy destroyer in Aden in early January 2000. That attack failed when the bomb boat sank under the weight of the explosives.

U.S. counterterrorism officials further described Khallad as the intermediary between alleged Sept. 11 mastermind Khalid Shaikh Mohammed and hijackers Khalid al-Mihdhar and Nawaf al-Hazmi. Mohammed was captured in Rawalpindi, Pakistan, in March.

In January 2000, Khallad met with the two eventual Sept. 11 hijackers in Kuala Lumpur, Malaysia.

The CIA had learned about the meeting, and asked Malaysian authorities to monitor it. The Malaysians learned who was there but not what was discussed.

The meeting gained much greater significance to American counterterrorism officials a year later, when investigators tied Khallad to the Cole plot. His known associates -- including al-Mihdhar and al-Hazmi -- suddenly took on new importance.

Despite their association with Khallad, the two operatives were not put on watch lists at U.S. ports-of-entry until months afterward, in late August 2001 -- an omission characterized by some in Congress as a critical failure. A listing would have prevented the two from being allowed into the United States, but the 17 others were largely unknown to U.S. authorities.

By the time the two hijackers made the list, they already were in the country, making the final preparations for the Sept. 11 attacks.

Another person at the January 2000 meeting would later be associated with terrorism suspect Zacarias Moussaoui, who traveled to Malaysia later that year. Moussaoui is accused of conspiring with the Sept. 11 plotters to commit terrorism.

Khallad was in Afghanistan for much of the planning of the Sept. 11 attacks and was believed to have moved to Pakistan after the Taliban fell, officials said. Khallad is often described as one-legged but is actually missing only his right foot.

The raids that netted Khallad "were solely a Pakistani operation," Cheema said. "We didn't say anything before now because we wanted to see whether we could make more arrests."

Police sources said the first lead came Monday when authorities stopped a pickup truck carrying explosives among sacks of potatoes. The three Pakistani militants who were arrested led police to a fourth Pakistani man, who was arrested Tuesday and led police to Khallad, the police sources said.

Pakistani authorities also recovered 330 pounds of explosives and a large quantity of weapons, according to a statement from Cheema's National Crisis Management Cell, which oversees Pakistan's anti-terrorist activities.

"The recovered items indicate the magnitude" of those planned attacks, the statement said.

Also captured in the raids that netted Khallad was a nephew of Khalid Shaikh Mohammed, Pakistani officials said. American officials had previously described Ali Abdulaziz as active in Al Qaeda operations.

Numerous Al Qaeda chiefs have been captured in Pakistan since the Taliban fell, as have hundreds of lesser fighters, Pakistani officials say. Many of Al Qaeda's remaining operational leaders are believed to be in Iran, and Usama bin Laden and his chief deputy are still thought to be hiding in the mountains between Afghanistan and Pakistan.

The Associated Press contributed to this report.