"(Mueller's)saying he can't give us copies of the proposed guidelines until they are finalized, but, of course, once they are finalized they are no longer proposed or subject to change," Senate Judiciary Committee Chairman Patrick Leahy, D-Vt., said at the start of the meeting.
Leahy said the committee was still waiting for answers from the Justice Department to questions asked in March.
Mueller focused on four aspects of the FBI -- intelligence, investigative techniques, technology and human capital.
Intelligence gathering isn't limited to counterterrorism threats, but also researching potential espionage or proliferation threats, he said. Each field office now has a group of agents, analysts, linguists and surveillance specialists who are the "operational arms of our intelligence program," he said.
New investigative guidelines soon will be in place for FBI field agents collecting, analyzing and sharing intelligence under an improved internal framework, Mueller said.
Technology improvements he outlined include phasing in Sentinel, a Web-based case management program and information technology programs allowing the FBI to communicate with its partners.
He said the agency has begun programs to target people with critical skills.
2014: The Year in Music [PHOTOS]