The second day of public hearings by the joint House and Senate intelligence committees investigating Sept. 11 intelligence failures saw administration officials trying to defuse charges that U.S. intelligence agencies had known about a plan by Al Qaeda to attack the United States by using airplanes as missiles.

Deputy Secretary of State Richard Armitage and Deputy Secretary of Defense Paul Wolfowitz said the United States was aware of the Al Qaeda threat in the country but had no indication of when or where an attack by jetliner would happen. 

"I don't recall any warning about the possibility of a mass casualty attack using civilian airliners," Wolfowitz said.

Former President Bush's national security adviser, Brent Scowcroft, and his Clinton counterpart Sandy Berger also testified. Berger said that after 1998, the Clinton administration took numerous steps to kill Usama bin Laden and crush Al Qaeda, but he contradicted published reports that the outgoing Clinton administration offered the incoming Bush team a war plan to go after Al Qaeda.

He also said that he heard of the possibility of airplanes being used as weapons as one of several possible threat scenarios.

"But I don't recall being presented with any specific threat information about an attack of this nature or any alert highlighting this threat or indicating it was any more likely than any other," he said.

The comments come just one day after the committee's inquiry staff director, Eleanor Hill, laid out a series of indicators that the intelligence community had regarding possible threats on U.S. territory that were either disregarded or under-evaluated. At least 12 involved the use of airplanes as weapons.

CIA spokesman Bill Harlow issued a statement Thursday disputing some aspects of Hill's report, particularly suggestions that the agency did not devote significant resources to fighting terrorism before the attacks. 

Harlow said the agency doubled personnel in its Counterterrorism Center between 1997 and last Sept. 11 to nearly 115 analysts and 200 field operatives. The center now has expanded to more than 800 people.

The joint intelligence committee's investigation was supposed to be the definitive inquiry into Sept. 11, but now two lawmakers are pushing for an additional independent commission to look into it, saying the committee can't finish the work by its February deadline.

"When we get this commission up and working and finish its work. We can say with much more confidence than we can say now ... this will never happen again," said Sen. Joe Lieberman, D-Conn.

"Having a commission composed of the most credible people in America so that the American people can be confident that not only do we know what happened and what caused it, but we are taking all necessary action to prevent a repetition in the future," said Sen. John McCain, R-Ariz.

The House has already approved creation of an independent commission. In the Senate, McCain and Leiberman plan to offer it as an amendment to legislation for a Homeland Security Department. Lawmakers in both parties predict it will pass overwhelmingly.

The White House opposes an independent commission, citing concerns about possible leaks and tying up officials involved in the fight against terrorism

Members of Congress say that they have not gotten adequate intelligence from intelligence agencies and need a more forceful push especially since it appears the intelligence community did have many more clues than had previously been acknowledged.

They also say the intelligence agencies need a squeeze especially since it turns out that two of the hijackers had rented an apartment from an FBI informant and nobody in the government ever knew about it.

Nawaf Alhamzi and Khalid Almidhar were first identified overseas by the CIA in January of 2000 as suspects to watch. In 2001, they rented an apartment in San Diego from the informant, but by time the CIA told the FBI about them, they had vanished. That was one month before the Sept. 11 attacks.

Armitage said that the day after intelligence agencies informed the State Department about the two men, every consular office worldwide had been alerted.

"If we had had the information sooner, it is reasonable to believe these two criminals would never have entered the country in the first place," he said.

Lawmakers are furious because they were only told about it in the last few weeks.

Fox News' Carl Cameron and The Associated Press contributed to this report.