In the hours and days after the Sept. 11 terror attacks on Washington and New York, Mueller increased the number of agents monitoring terrorism to 6,000 -- six times the usual number -- but now the level has been reduced.
"That has leveled off to 2,000 (agents) right now," he said.
In his opening statement, Rep. Frank Wolf, R-Va., who chaired the House Appropriations hearing, said he hoped the new effort would not infringe on legal protections for citizens.
"In our quest to create a better, faster, more agile FBI, we have to be careful not to trample on the rights granted to every American under the Constitution," Wolf said.
But Mueller said that the reforms would include training for agents to prevent any loss of civil liberties.
"Agents understand the consequences of going beyond the Constitution," Mueller said.
Mueller has proposed moving 518 agents away from drug enforcement and organized crime investigations and have them focus primarily on homeland security and international fights against terrorism. He would also develop a joint terrorism taskforce with the CIA and Immigration and Naturalization Service to coordinate investigations.
He has also proposed hiring 900 new agents.
Both the FBI and CIA have been under criticism for failing to work together to prevent the September attacks. Mueller said the reforms should help improve the coordination between agencies and help equip FBI agents with the necessary power to fight terrorism.
Revelations that agents in Phoenix and Minnesota noticed suspicious activity at various flight schools used by the hijackersm, but were not heeded by headquarters supervisors, angered lawmakers and the public.
President Bush has proposed a new cabinet-level agency for Homeland Security to improve coordination between agencies, although many lawmakers are skeptical that unless the FBI and CIA are put under the authority of the new agency, the coordination will not improve. The current proposal would leave the agencies reporting directly to the president.