Associated Press President Bush talks with reporters outside the doors of the National Security Operations Center, during a tour of the top secret National Security Agency in Fort Meade, Md., yesterday.

WASHINGTON ÷ President Bush said yesterday the CIA and FBI did not communicate adequately with each other about possible clues to a terrorist attack before Sept. 11, as Congress began a rare closed-door series of investigative hearings to determine why such intelligence failures occurred.

ãWe need to be aggressive and rigorous in this inquiry, asking the right questions like who knew what? And if they didnât know it, why? And what did they do with the information they had?ä Sen. Barbara Mikulski, D-Md., said yesterday as she walked past reporters into the room, off-limits to the public, where the joint House-Senate intelligence committee began its hearings.

Other congressmen filed by without speaking to reporters. Mikulski and other lawmakers said they expected most of the first day to be taken up with procedural details, such as how the committee would organize its work.

Bush, speaking at the National Security Agency just hours before the inquiry began, asserted there is no evidence U.S. officials could have averted the attacks, even if the two agencies had worked together better.

ãIn terms of whether the FBI and CIA communicated properly, I think itâs clear that they werenât, and now weâre addressing that issue,ä the president said. ãI see no evidence today that said this country could have prevented the attacks.ä

The investigation has been compared to the governmentâs inquiry into how the United States missed preparations for Japanâs surprise attack on Pearl Harbor. The last large-scale investigation of intelligence matters was the commission set up by Sen. Frank Church in 1975, which led to new congressional oversight of the CIA.

In the latest revelation of missed clues, a CIA official said both the CIA and FBI knew as early as January 2000 that one of the eventual Sept. 11 hijackers, Khalid Almihdhar, would be attending a meeting of suspected al-Qaida members.

Bush, in the appearance at the NSA, renewed his support for the intelligence committeesâ investigation, but again objected to calls in Congress for a separate, independent inquiry. That could hinder efforts to prevent future terrorist strikes and jeopardize U.S. intelligence sources, Bush said.

Meeting in soundproofed, secure rooms at the Capitol, lawmakers will take stock of an intelligence community that overlooked clues and didnât always share information it had about the hijackers. The closed-door hearings began yesterday and will go public June 25. Mikulski said lawmakers owe it to the victims of Sept. 11 to run a ãserious, thorough and credibleä inquiry to ensure such intelligence lapses do not recur.

ãWe will certainly be able to improve the capabilities that we have to focus more on the threats that actually exist,ä Rep. Porter Goss, R-Fla., House Intelligence Committee chairman, said yesterday on NBCâs ãToday.ä ãThatâs going to happen, but Americans are always going to have to have a little vigilance.ä

Rep. Nancy Pelosi of California, that committeeâs top Democrat, said one purpose of the hearings is to ensure federal law enforcement agencies donât react the wrong way and spy more on Americans.

ãI think we have to be smarter, more clever and protect the people in a way that also protects civil liberties and the Constitution,ä Pelosi said yesterday on CNN.

The intense scrutiny has led to fingerpointing between the CIA and FBI.

Over the weekend, government sources said the CIA had important information in early 2000 about two of the future hijackers, Almihdhar and Nawaf Alhazmi, both of whom attended a mid-January 2000 meeting in Malaysia.

Responding to the disclosure, a CIA official, speaking Monday on condition of anonymity, disputed reports that the agency had kept that information from the FBI. The CIA official said two FBI officials were briefed on Almihdhar.

Neither agency gave the information enough significance to alert authorities to watch for Almihdhar or Alhazmi at U.S. points of entry until three weeks before the attacks, when the CIA, alerted to a large al-Qaida operation in the offing, added the two men to a watch list that INS and State officials use. By this time, however, they were already in the country.

Almihdhar, in fact, had been in and out of the United States several times. The U.S. government had given him a multiple entry visa enabling him the freedom to come and go as he pleased. Both hijackers were aboard American Airlines Flight 77 that crashed into the Pentagon.

FBI officials declined comment Monday night, saying Director Robert Mueller did not want to engage in fingerpointing.