MANHATTAN, Kan. -- On the same day the FBI was criticized for years of failing to respond to the growing threat of terrorism, agency director Robert Mueller insisted the agency has now made anti-terrorism its No. 1 priority.

"We in the FBI have committed ourselves to making the fundamental changes necessary to combat evolving threats that target our country," Mueller said in a speech Tuesday at Kansas State University.

"We have made progress and we will continue to meet -- and to defeat -- all threats against the security of our nation and its citizens."

Mueller's predecessor, Louis J. Freeh, and Attorney General John Ashcroft appeared Tuesday before the commission investigating the attacks. In a written report, the commission criticized the FBI for what it called a failure to reorganize and respond to the growing threat of terrorism.

Mueller acknowledged that before Sept. 11 "there were areas where we needed to improve."

"There were things we could have done better," he said in answer to a question from the audience. "We have moved since Sept. 11 to right those things we could have done better."

Mueller is expected to testify Wednesday before the commission.

"Immediately following 9-11, the FBI's number one priority became the prevention of terrorist attacks," Mueller said in his speech. "This required a systematic approach examining all aspects of bureau operations."

He said investigations of terror threats previously were centered in the FBI field office where they began. "Now the FBI operates under centralized management of our counterterrorism program," he said.

The agency has upgraded its technology, reworked its administration to make it "more efficient and more responsive," and increased recruiting efforts, particularly for people with backgrounds in computer science, Middle Eastern studies or foreign languages.

He said the FBI also has doubled the number of agents and analysts in counterterrorism, added about 450 translators and created special units to deal with terrorist threats.