The CIA wants to get inside Khalid Shaikh Mohammed's head.

But his interrogators -- CIA, FBI or from a foreign security service -- are working against the clock. Mohammed's information about impending terrorist operations and the location of Al Qaeda leaders and cells grows more dated by the hour.

Whether the CIA can learn anything useful from the alleged Sept. 11 mastermind depends on the skills and methods of the interrogators, Mohammed's willingness to talk and perhaps simply time.

Captured early Saturday in a raid in Pakistan, he is now believed to be in U.S. custody overseas.

Of top priority during the questioning is gaining intelligence that could help quickly disrupt attacks being planned or lead to added precautions, American counterterrorism officials said.

That could mean a domestic law enforcement raid to break up a cell ready to strike, or an increase of security at areas Mohammed names as targets subject to imminent attacks. Intelligence about Mohammed's activities led in part to the orange alert that lasted most of February, counterterrorism officials said.

Overseas, it could mean an operation that leads to the capture of Al Qaeda leader Usama bin Laden.

But such information is just what he is most likely to try to keep secret, or lie about. Still, terrorists who learn of Mohammed's capture may alter their plans, abandon safe houses or make hurried telephone calls -- actions that could expose them to detection.

The only Al Qaeda capture that approaches the magnitude of Mohammed's was that of Abu Zubaydah last March. Zubaydah more than once provided information that sent American security officials scurrying to provide warnings to cities and sectors of the economy, knowing all the while that he could be lying.

Zubaydah did provide some information that was later verified through other sources, officials said. That included intelligence that led to the detention of Jose Padilla, the American whom federal officials allege was plotting to use a radiological weapon on U.S. soil.

U.S. officials were elated by Mohammed's capture.

"This is equal to the liberation of Paris in the second World War," said GOP Rep. Porter Goss of Florida, chairman of the House Intelligence Committee, on ABC's "This Week."

"This is a giant step backward for the Al Qaeda," Republican Sen. Pat Roberts of Kansas, chairman of the Senate Intelligence Committee, told "Fox News Sunday." "Now their operations commander is simply out of operations."

Officials were not releasing details of Mohammed's detention. Previous high-level Al Qaeda captives have not been brought to U.S. soil; they would have rights not afforded on foreign soil, U.S. officials say. Where they are, however, has not been disclosed.

Another secret is how officials will attempt to get information from Mohammed.

U.S. officials insist they eschew physical, violent torture, although it is unclear if all of America's allies live by a similar code.

Also less clear are to what extent interrogators use certain methods that human rights groups also regard as torture: sleep deprivation, threats of torture and other techniques intended to confuse, frighten or wear down a captive.

"We don't sanction torture but there are psychological and other ways that we can get most of what we need," said Sen. Jay Rockefeller, D-W.Va., vice chairman of the Senate Intelligence Committee.

Whatever the method, the goal is to get inside a prisoner's head and get him talking, experts say. An interrogator may try to appeal to Mohammed's vanity, his fears, or whatever lever seems to offer the best avenue to getting information that will stop terrorist attacks.

As his interrogation moves away from the immediate, Mohammed can provide counterterrorism officials with a deeper understanding of Al Qaeda and its history.

Officials believe he can detail how Sept. 11 was put together, answering long-standing questions about the plot's origins: Who chose the World Trade Center and Pentagon as targets? Who picked Sept. 11 as the date?

American officials say Mohammed, who was born in Kuwait and has both Pakistani citizenship and ancestry, planned and coordinated key aspects of the Sept. 11 operation.

His information can be cross-checked with Ramzi Binalshibh's, his former aide who was captured in September. Binalshibh was a part of the cell that included Mohamed Atta, chief among the Sept. 11 hijackers.

In the mid-1990s, Mohammed also worked with his nephew Ramzi Yousef and two others in the Philippines on a number of operations. Yousef is in prison for his role in the 1993 World Trade Center bombing.

One plan called for bombing up a dozen trans-Pacific airliners in flight. A second involved crashing an airplane into CIA headquarters outside of Washington. Officials have suggested these plots -- broken up in their infancy with the arrests of Mohammed's associations -- were the seeds of Sept. 11.

The four plotters were linked to Al Qaeda through a financial operative named Khalifa, who is bin Laden's brother-in-law, officials have said. Khalifa is believed to remain at large.