During a visit to the wounded symbol of American military might, Bush thanked weary rescuers at the Pentagon and at the destroyed World Trade Center in New York for forging ahead with their search even as hopes faded of finding survivors.

''Coming here makes me sad, on the one hand. It also makes me angry,'' Bush said after spending a full minute staring at the Pentagon's ripped side. Like a sad game show host, he turned to reporters and waved a hand back toward the building's roof, which drooped at an angle over the hole, four stories collapsed atop each other.

''I'm overwhelmed by the devastation,'' he said. To give an idea of the power of the impact when American Airlines Flight 77 hit the building Tuesday, Bush said Defense Secretary Donald H. Rumsfeld felt the explosion in his office - on the opposite side of the massive five-sided structure.

''The building rocked. And now I know why,'' Bush said.

The military said Wednesday that about 150 people, military and civilian, were missing from the crash, which carried 64 passengers and crew to their deaths.

Bush said with the help of its people the United States, which remained on ''high alert for possible activity,'' will recover from its terror ordeal. He particularly thanked those who have given blood and those who are praying for the victims and their families.

''The nation mourns, but our government will go on,'' Bush said. ''Our country, however, will not be cowed by terrorists, ... by people who are willing to destroy people's lives because we embrace freedom.''

The Pentagon's appearance was somber, its windows coated in soot, some blown out completely. Two trees beside the point of impact were blackened, twisted, devoid of leaves.

Just above the gash, a lone American flag waved at full staff. A dozen workers in yellow hard hats unfurled a larger Star-Spangled Banner beside it. Their colleagues applauded, and broke into a somber rendition of ''God Bless America.''

The president offered his first attention to soldiers in camouflage fatigues, some of whom saluted him. He and Rumsfeld then greeted a melange of firefighters, police officers, soldiers in black berets and a chaplain in a white sport shirt.

Bush said he came to the crash site to offer thanks to the workers digging out the ruins of the Pentagon and the Twin Towers of the World Trade Center that were leveled by coordinated suicide jetliner attacks.

''Coming here confirms what the secretary and I both know, that this is a great nation,'' Bush said. ''People out here are working their hearts out to answer families' questions, to remove the rubble and debris from this office.''

A few workers continued to collect debris and put it into a dump truck throughout Bush's visit, their cranes and power equipment whirring. All the crews returned to work as Bush's motorcade pulled off to Rumsfeld's office on the other side of the building in suburban Arlington, Va.

Inside, Bush stood in a hallway and greeted about 200 civilian and military staff who work at the Pentagon. Then he met with Rumsfeld and military commanders for an update on recovery efforts.