By Alan Elsner, National Correspondent

NEW YORK/WASHINGTON (Reuters) - President Bush committed the United States to a ``monumental struggle of good versus evil'' on Wednesday as emergency workers dug desperately for survivors from the worst attack on the country since Pearl Harbor and began the search for bodies.

As the nation tried to move back to a semblance of normal life, Americans also braced themselves for a death toll expected to climb well into the thousands from the attacks.

Knife-wielding hijackers commandeered four planes on Tuesday and flew two into New York's World Trade Center, toppling the two highest structures in the city; a third seriously damaged the Pentagon. The fourth hijacked plane crashed in Pennsylvania.

``The numbers that we're working on are in the thousands. Obviously we hope that's not the case,'' said New York Mayor Rudolph Giuliani.

``The best estimate we can make, relying on the Port Authority and just everybody else that has experience with this, is there will be a few thousand people left in each building,'' he said, referring to the two massive twin towers of the World Trade Center where 40,000 worked.

Fire Chief Edward Plaugher, in charge of fighting the fire at the Pentagon, said early on Wednesday the death toll at the U.S. military headquarters could range from 100 to 800 people. He said the fire was still not fully under control and it would be days before a precise figure was known but no more survivors were expected to be found.

Mayor of New York City, Rudy Giuliani, said at least 202 firefighters were still missing and 259 uniformed service members had not been accounted for. They had apparently rushed into the first of the towers to be hit and were caught inside when it collapsed.

The mayor said rescue workers were in voice contact with at least one more person trapped in the rubble. ``They are trying to rescue him and get him out,'' he said.

DEFINING MOMENT FOR BUSH

Bush, facing the defining moment of his eight-month-old presidency, called the attacks ``an act of war'' which he vowed to win.

``This battle will take time and resolve, but make no mistake about it we will win,'' he said.

Americans reacted with controlled fury and a burst of patriotism as the full dimensions of the devastation and the human toll began to emerge. The country was still far from functioning normally with airports and financial markets shut down and many schools closed.

The first clues began to emerge about the identities of the perpetrators, pointing toward a possible Middle Eastern and Islamic connection.

Two Boston newspapers reported that authorities in Massachusetts had identified five Arab men as suspects and had seized a rental car containing Arabic-language flight training manuals at the city's Logan International Airport, where two of the hijacked planes originated.

Investigators found a copy of the Koran, a videotape on how to fly commercial jets and a fuel consumption calculator in a pair of bags meant for American Airlines Flight 11, which crashed into the World Trade Center, the Boston Globe said.

The Boston Herald said the suspects entered the United States from Canada. Two of the men were brothers whose passports were traced to the United Arab Emirates, and one was a trained pilot.

EVIDENCE POINTS TO ISLAMIC GROUP

The discovery, if verified, would be the latest piece of evidence pointing investigators toward Islamic extremists. Senior U.S. officials have said initial evidence points to the organization of Osama bin Laden, the Saudi-born dissident now living in Afghanistan who is blamed for bombing two U.S. embassies in East Africa and other anti-American attacks.

U.S. agents served warrants on homes and searched businesses in south Florida, and issued alerts for two cars in connection with the attacks, local media reported.

As a cloud of dust still hung over New York City, rescue workers pulled a handful of people out of the wreckage of the World Trade Center on Wednesday morning and reported signs of life in the rubble, including at least one person sending out calls on a cellphone.

The world's financial center resembled a desolate war zone, the streets of lower Manhattan coated in gray ash and a thick trail of brown smoke pouring into the sky from where the World Trade Center's twin towers once stood.

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