The director of the CIA told Congress yesterday that he takes "ultimate responsibility" for the accidental bombing of the Chinese Embassy in Belgrade and promised to change the agency's procedures to ensure that such a mistake cannot happen again.

In his first public testimony about the May 7 incident, Director of Central Intelligence George J. Tenet said the airstrike by a U.S. B-2 bomber was aimed at a Yugoslav arms agency, which was the first and only target selected by the CIA during NATO's entire 78-day bombardment of Yugoslavia.

Most of the approximately 900 targets struck during the war were chosen by NATO and the U.S. military's European Command. But as NATO forces began to run short of sites to bomb, U.S. intelligence agencies were invited to propose targets as well.

Tenet attributed the error, which cost the lives of three Chinese citizens and wounded more than 20, to poor targeting procedures, inadequate review and faulty databases -- all factors previously explained in detail to the Chinese government by the Clinton administration.

"It was a major error," Tenet told the House Permanent Select Committee on Intelligence. "I cannot minimize the significance of this."

Although the CIA had occasionally helped the military in some aspects of targeting, Tenet said the Yugoslav Directorate of Supply and Procurement was the first target "unilaterally proposed and wholly assembled" by the spy agency.

Tenet's assertion was challenged by Patrick G. Eddington, a former CIA photo analyst who attended the hearing and said afterward that he had participated in the identification of numerous military targets as a member of the CIA's Combined Targeting Support Staff.

A CIA spokesman responded that the targeting support staff exists to help the military select targets, not "develop" targets from start to finish.

Tenet and Deputy Secretary of Defense John J. Hamre, who joined the CIA chief at the witness table, also provided new details about a mid-level intelligence analyst at the CIA who questioned the targeting data before the airstrike.

The analyst was not involved in the agency's targeting process but voiced concerns to those who were, Tenet said.

The analyst also expressed his doubts in a telephone call on May 4 -- three days before the strike -- to an officer at the European Command's targeting task force in Naples, Italy. The analyst then left for a two-day training exercise, without realizing that the arms agency had been placed on a list for destruction, Tenet said.

When the analyst returned from the training exercise on May 7 and saw the arms agency on that day's target list, he again called Naples. But the officer with whom he spoke apparently believed the analyst was only questioning whether the targeted building was the arms agency's central headquarters, not whether it belonged to the arms agency at all.

"Neither of them went up the chain to try to turn off the strike," Hamre said, "because they didn't think they needed to."