Attorney General Alberto Gonzales (search) has been on the job for several days already, but Monday's ceremonial swearing-in gave President Bush the chance to push for renewal of the USA Patriot Act (search).
Parts of the anti-terror law enacted shortly after the Sept. 11, 2001, terror attacks are set to sunset at the end of this year. The administration wants Congress to extend those portions and even desires to expand some rules.
"We must not allow the passage of time or the illusion of safety to weaken our resolve in this new war" on terrorism, Bush told about 300 Justice Department officials attending the ceremony.
The Patriot Act bolstered FBI (search) surveillance and law-enforcement powers in terror cases, increased use of material witness warrants to hold suspects incommunicado for months and allowed secret proceedings in immigration cases.
Civil liberties groups and privacy advocates lambasted the law because they said it undermines freedom. But Bush said the act "has been vital to our success in tracking terrorists and disrupting their plans."
He added that the new attorney general now joins every employee at the Department of Justice in the urgent mission of protecting the United States from another terrorist attack.
Gonzales, who has vowed to fight terror and confront injustice, was sworn in by Supreme Court Justice Sandra Day O'Connor (search) and is expected to fight to extend the sunsetting provisions created in part by his predecessor, John Ashcroft (search). Ashcroft attended the ceremony.
Gonzales also answered critics who have suggested he is too close to the president to protect interests of Americans from bad administration policies.
"Undeniably, the attorney general is a member of the president's Cabinet, a part of his team. But the attorney general represents also the American people, and his first allegiance must always be to the Constitution (search) of the United States," he said.
"I am confident that in the days and years ahead we in the department will work together tirelessly to address terrorism and other threats to our nation and to confront injustice with integrity and devotion to our highest ideals," he added.
Gonzales reinforced remarks he made during the confirmation process in which he explained that his work as White House counsel, in which he helped develop policy on interrogating enemy combatants, does not prevent him from being an instrument in the battle for freedom and protection of individual rights.
Bush reinforced that Gonzales' mission is to ensure equal justice for every American beyond the War on Terror, and he lauded what he said is his outstanding character.
"I've witnessed his integrity, his decency, his deep dedication to the cause of justice. Now he will advance that cause as the attorney general and ensure that more Americans have the opportunity to achieve their dreams," he said.
The president also credited Ashcroft with making the nation safer and overseeing a drop in violent crime outside of terror-fighting.
Gonzales, who has been a close adviser to the president for about a decade, is now the 80th attorney general of the United States and the first Hispanic-American in the job.
FOX News' Mike Emanuel and The Associated Press contributed to this report.