The National Security Agency intercepted two messages on the eve of the Sept. 11 attacks on the World Trade Center and the Pentagon warning that something was going to happen the next day, but the messages were not translated until Sept. 12, senior U.S. intelligence officials said yesterday.

The Arabic-language messages said, "The match is about to begin" and "Tomorrow is zero hour." They were discussed Tuesday before the House-Senate intelligence committee during closed-door questioning of Lt. Gen. Michael V. Hayden, director of the NSA, the agency responsible for intercepting and analyzing electronic messages.

Intelligence officials said the two messages -- even if translated on Sept. 10 -- would not have provided enough information to prevent the attacks. But their disclosure put the NSA in the spotlight for the first time since reports of intelligence failures began to emerge this spring and seemed likely to sharpen the focus of the congressional investigation -- which has been dominated by concerns about the performance of the FBI and the CIA -- on problems at the nation's premier eavesdropping agency.

U.S. intelligence sources said NSA analysts are not certain who was speaking on the Sept. 10 intercepts. They came from sources -- a location or phone number -- that were of high-enough priority to translate them within two days but were not put in the top priority category, which included communications from Osama bin Laden or his senior al Qaeda assistants.

"There had been a lot of chatter up there indicating something was up," a senior administration official said. "But it does not say where, what and how reliable."

The official said the messages appear dramatic in hindsight but added: "If you had it on September 10th, what does it tell you that is actionable?"

The NSA declined to comment on the intercepts. "I have no information to provide," NSA spokeswoman Judy Emmel said.

The agency provided classified information to the joint intelligence committee more than a month ago about the messages and the failure to get them translated until after Sept. 11. The messages, and the translating delay, became the subject of discussions between the congressional staff and intelligence officials before Tuesday's hearing, which in addition to Hayden included testimony by CIA Director George J. Tenet and FBI Director Robert S. Mueller III, according to congressional and administration sources. The three men appeared before the panel again yesterday.

CNN first reported on the committee's discussion of the messages yesterday.

The NSA, based at Fort Meade, is one of the government's most secretive intelligence agencies. It intercepts more than 2 million electronic communications an hour -- telephone conversations, e-mails, Internet traffic -- from satellites and listening posts around the world.

Although the NSA consumes an estimated $6 billion of the $30 billion the government budgets for intelligence each year, and spends most of it on high-tech interception equipment, the agency does not have adequate means to filter out the millions of bits of irrelevant information it scoops up each day. Intelligence budgets are classified.

Without such filters, human translators must sort through mountains of data, and only a fraction of the foreign-language material is translated promptly. Much is never analyzed.

Analysts said the fate of the Sept. 10 intercepts points to a broader aspect of the effort to improve intelligence gathering: technology vs. humans. More than the CIA, the NSA has been criticized for failing to put sufficient emphasis on employing enough skilled translators and analysts to decipher what it collects.

Many observers of the intelligence system credit Hayden, who was appointed director of the agency in March 1999, with recognizing the problem and trying to fix it.

Over the past several years, the House and Senate intelligence panels have criticized the NSA's failure to modernize its operations as communications technologies have become more sophisticated. Computers that over the past decade were used to scan messages for certain key words have proved much less effective as targets have changed from official Russian military and intelligence transmissions to those of individual terrorists and terrorist groups around the world.

Congress has added money to the NSA budget in recent years, and Hayden has assembled a major renovation plan for the agency, but Congress has questioned whether it is satisfactory.

Since Oct. 4, when British Prime Minister Tony Blair announced in a speech before the House of Commons that "a range of people were warned to return back to Afghanistan because of action on or around September 11th," stories have appeared in the media that a warning message had not been taken seriously or translated by the NSA.

A senior intelligence official said yesterday it was still unclear what information Blair was referring to. There have been references in published reports to a message to bin Laden's mother shortly before Sept. 11 that she should return to her home in Saudi Arabia, but U.S. intelligence officials denied having evidence that it existed.

This month, after material was sent to the congressional intelligence panels, several stories appeared, including one that said the chief hijacker on Sept. 11, Mohamed Atta, was overheard talking to a senior bin Laden figure before boarding an airplane. NSA and other intelligence officials denied that report but never indicated there were less precise messages that had not been translated.

The House-Senate panel apparently has decided to delay hearing in an open session testimony by Mueller, Tenet and Hayden, originally set for next week. "We want to make sure when we go public that the right people are there and we're prepared so we don't look like we're flying by the seat of our pants," said Rep. Ray LaHood (R-Ill.), a member of the panel.

Staff writer Juliet Eilperin contributed to this report.