WASHINGTON - The CIA says in a classified chronology submitted to Congress recently that it picked up the trail of a al-Qaida operative who turned out to be a Sept. 11 hijacker months earlier than was previously known, government officials said yesterday.

The officials said that the CIA learned in early 2001 that Khalid al-Midhar, who died in the attack on the Pentagon, was linked to a suspect in the bombing of the Navy destroyer USS Cole in October 2000. The agency had said previously that it did not learn of Midhar's Qaida connections and multiple visits to the United States until the month before the hijackings, when an increase in "chatter" about terrorist threats prompted a review of the CIA's terrorism files.

CIA officials also neglected to advise the FBI and other agencies when it learned of Midhar's connections to the terrorist group, the officials said. As a result, he was not put on any government watch list until after the August review, enabling him to enter the country unhindered. The State Department routinely renewed his visa in June 2001 after it expired.

The performance of agencies like the FBI and CIA is under intense scrutiny as the House and Senate intelligence committees prepare for hearings, starting Tuesday, into the lapses that led to the Sept. 11 debacle.

Much of the criticism to date has focused on the FBI, and yesterday's disclosures about the CIA's knowledge, reported in this week's issue of Newsweek, are the first time the CIA's actions have been questioned.

In separate appearances on television talk shows yesterday, Attorney General John Ashcroft and the FBI director Robert S. Mueller III defended their handling of their own investigations and said they were cooperating fully with Congress, passing tens of thousands of documents to the committees.

The CIA's discovery that Midhar could be tied to Qaida terrorism was an important one, the government officials said. If other agencies had known it, the information might have led to the discovery that Midhar and an associate he lived with in California, Nawaq Alhazmi, had attended flight schools in the United States.

As a result, when an agent in Phoenix warned FBI headquarters in July 2001 that Osama bin Laden's followers might be attending aviation schools this country in preparation for terror attacks, the agency did not realize that Midhar and Alhazmi had also taken such flight training.

One intelligence official said the failure of the CIA's sharing of its information would most likely not have prevented the Sept. 11 attacks. "The notion that this would have changed history or rolled up the hijacking plot is highly speculative," the official said.

But such communications breakdowns in the months before the Sept. 11 attacks have led some officials, including Mueller, to say that a better sharing of information might have led authorities to thwart the Sept. 11 attacks.

The CIA first learned of Midhar and Alhazmi in 2000, after the men were identified as participants in a January 2000 meeting of suspected terrorists in Malaysia. Sometime in 2000 the agency also learned that both men had visited the United States, Midhar on several occasions. But it did not understand the men's significance until after the Cole bombing in October 2000. By late that year or early the next, it had connected Midhar with an al-Qaida suspect in that attack. The CIA then learned that Midhar had entered the country multiple times before the Cole bombing.

Yet it wasn't until Aug. 23, 2001, after the CIA's review of its terrorism files, that the names of the two men were passed on to the Immigration and Naturalization Service. By then, the INS found that they had already entered the country. The FBI began an investigation and was still searching for the two men when the hijackings occurred.

With congressional hearings beginning this week, the intelligence agencies are preparing their cases to show why they failed to detect the plot that destroyed the World Trade Center and damaged the Pentagon.