WASHINGTON - The Bush administration promised yesterday an intense and prolonged military campaign in a "global assault" against terrorism as officials signaled that credible threats exist of immediate attacks against more U.S. targets.

President Bush is scheduled to tour the devastated site of the toppled World Trade Center towers on the southern tip of Manhattan this morning. He declared today a national day of prayer and remembrance.

But yesterday, his administration seemed intent on preparing the country for war.

Talking to reporters in the Oval Office, he said, "I'm a loving guy. And I am also someone, however, who's got a job to do, and I intend to do it."

For the first time, a senior administration official, Secretary of State Colin L. Powell, openly identified Osama bin Laden, a Saudi billionaire and terrorist mastermind who has been given sanctuary in Afghanistan, as a prime suspect in the assaults. He said the United States will present its case against that group to the world.

"And at that point, we will go after that group, that network and those who have harbored, supported, and aided that network, to rip the network up," he said. "And when we're through with that network, we will continue with a global assault against terrorism in general."

Officials sharpened their estimates of the number killed in the suicide attacks. More than 5,000 people are thought to have been killed in Tuesday's attacks, including those aboard the doomed flights and those who perished on the ground. That is more than double the number killed in the Japanese attack that drew the United States into World War II in 1941.

The estimated death toll from Tuesday included 190 at the Pentagon and 4,763 who were reported missing by New York Mayor Rudolph W. Giuliani. There were 266 people aboard the planes.

In New York and Washington, rescue workers held out hope of finding survivors among the rubble, while investigators had some success tracking down more supsects in the United States and abroad.

ABC News reported last night that 10 people were detained at John F. Kennedy and La Guardia airports in New York after authorities discovered them carrying fake identification, knives and certificates from a Florida flight school used by the men who crashed two commercial airlineers into the World Trade Center on Tuesday.

Five of the detained men reportedly had tried to board a plane around the time of Tuesday's hijackings but were turned away.

At a briefing last night, FBI officials denied that the detained men were carrying weapons or fake flight certificates and said that only false identification was found.

They confirmed that "a number" of people have been taken into custody since Tuesday and held for immigration violations. They were in the custody of the Immigration and Naturalization Service, a Justice Department official said. Some of them could be charged today, which would enable officials to detain them beyond tonight, which would otherwise be the deadline for releasing them.

Investigators also made headway at the crash sites, recovering a "black box" data recorder from the airplane that went down in Pennsylvania.

They also picked up a signal from a black box in the jet that smashed into the Pentagon and hope to recover that device today.

FBI Special Agent Bill Crowley said the recorder in Pennsylvania was found about 4:20 p.m. in an 8-foot crater caused by the crash. Crowley said the recorder will be analyzed by the National Transportation Safety Board in Washington. "We're hoping it will have some information pertinent to what happened on the plane," Crowley said. "This development is going to help a lot."

FBI officials also said they have obtained transcripts of conversations between pilots on the flight and a control tower.

German connection

In Germany, investigators said yesterday that three hijackers aboard the planes in the U.S. terror attacks once lived in Hamburg and were part of an organization formed this year to destroy U.S. targets.