WASHINGTON — WASHINGTON -- President Bush offered new hope of prosecution in the Rodney King beating case last night while ordering federal troops into riot-torn Los Angeles to put down the "mob violence" that resulted from the acquittal of four police officers. Mr. Bush, whose re-election depends in part on whether Americans trust him to maintain domestic tranquillity, said last night that that responsibility was foremost on his mind. "I will use whatever force is necessary to restore order," the president said in a televised address from the Oval Office. "As your president, I guarantee you this violence will end." Mr. Bush also answered appeals from black leaders, who urged him to uphold his constitutional responsibility to establish justice by empowering a federal grand jury to investigate whether civil rights charges could be brought against the Los Angeles police officers who were videotaped beating motorist Rodney King. "The verdict Wednesday was not the end of the process," he said, indicating he was confident that federal indictments would likely result. "I am confident that in this case, the Justice Department will act as it should," he said. "The federal effort in this case will be expeditious and it will be fair. It will not be driven by mob violence but by respect for due process and rule of law." As he has since the beginning of the national turmoil that followed the King verdict Wednesday, Mr. Bush indicated he was torn between "two big issues that have collided on the streets of Los Angeles . . . violence in our cities and justice for our citizens." But the incident gave him the opportunity to demonstrate leadership in handling the crisis, and he made the most of it last night with a take-charge approach not seen at the White House since last year's days of Operation Desert Storm. Earlier in the day, Mr. Bush dispatched a federal force of 5,000 military and civilian peacekeepers to the riot scene, where the death toll now exceeds the worst days of the turbulent 1960s. Last night he ordered the military contingent, 2,500 soldiers and 1,500 Marines, into action to help local police and firefighters restore order to the city. At the same time he federalized the National Guard troops already deployed so their efforts could be coordinated. Mr. Bush also sent 1,000 civilian law enforcement officers, includingSWAT teams and riot police from the Border Patrol, the Bureau of Prisons and the U.S. Marshals Service. The White House stressed that the president had decided to mobilize the federal forces at the request of California Gov. Pete Wilson and with the concurrence of Los Angeles Mayor Tom Bradley. The soldiers and Marines, expected to arrive sometime last night, were coming in full battle dress. They were to be carrying carrying rifles or sidearms, with bayonets and gas masks at the ready. They were also bringing along machine guns but would not set them up without receiving further orders, Pentagon officials said. It was the first time Mr. Bush had ordered the domestic use of federal forces since September 1989, when 1,100 troops were dispatched to the hurricane-ravaged U.S. Virgin Islands to halt a frenzy of looting and violence. Use of troops was generally supported by the black leaders who metwith Mr. Bush yesterday morning. Many said they feared the picture of blacks looting and killing was creating a white backlash that would further polarize the nation. But they argued it was equally important for Mr. Bush to get the beating case before a federal grand jury quickly. They said it would send what the Rev. Joseph P. Lowery, head of the Southern Christian Leadership Conference, called a "message of hope to cool the tempers" in riot-torn communities. The Rev. Benjamin L. Hooks, executive director of the National Association for the Advancement of Colored People, said Mr. Bush "is beginning to recognize the fact that unless we deal with this issue, America is in for a long, hot summer ahead." "We reminded the president that for 14 months the black community had been very patient, waiting on the American justice system to act," Mr. Hooks said. "And it failed us miserably."