9/11 Was 'Zero Day' in Intercepted Warning

June 20 -- The National Security Agency intercepted two messages the day before Sept. 11 where the participants referred to "zero day" and beginning of "the match," intelligence sources told ABCNEWS.

The public disclosure of the information has angered the White House, which says it compromises national security.

The NSA, sources said, secretly intercepted and recorded two conversations in Arabic on Sept. 10. One said, "Tomorrow is zero day." Another intercepted message said, "The match begins tomorrow."

However, the information was not translated until after the attacks — on Sept. 12 — and, sources said, even if the messages had been translated sooner, it would not have been of much use because the messages were too vague and had no context, with no details of time, location or the nature of the event referred to.

The sources did not consider the information to be a smoking gun, and described it as the sort of chatter that is intercepted constantly, and is seldom of use.

However, two weeks ago, one source told ABCNEWS the information National Security Agency officials received was the kind of thing that might have prompted an alert, if it had been known to other parts of the law enforcement and intelligence communities.

The NSA often has a lag in translating information, and was too overwhelmed with data to translate the two messages before the attacks, sources said.

Part of the problem is that the agency, which coordinates, directs, and engages in specialized activities to protect U.S. information systems and produce foreign intelligence information, gets millions of pieces of information, and does not have enough analysts to search through it all and interpret it. It often takes a couple of days to make translations.

Anger Over Disclosures

Now that the translations are available, the White House expressed anger that word of the messages has reached the public and blamed a congressional probe for leaking the information.

"The president has deep concerns about the inappropriate disclosure of information that can compromise both sources and methods and potentially interfere or harm America's capacity to fight the war against terror," White House spokesman Ari Fleischer said. "Information that is being provided to these [congressional] committees is extraordinarily sensitive."