MORE ON THIS STORY FULL COVERAGE • America Under Attack VIDEO • Hijacked Plane Hits First Tower • Hijacked Plane Hits Second Tower • Complete Video Coverage of the Attacks IN DETAIL • World Trade Center Attack • Terror Strikes America • World Trade Center Slideshow COMMUNITY • Your Reaction to the Terrorist Attacks RELATED STORIES • Suspects ID'd; Rescue Efforts Continue

"It makes me sad on the one hand," the president told rescue workers. "It also makes me angry. Our country will, however, not be cowed by terrorists."

Before the president's tour, firefighters had finally extinguished the fires and draped a massive American flag near the collapsed wing of the building to welcome him. Rescue workers searching the remains of the damaged wing all but lost hope of finding any survivors. Officials now estimate the number of dead or missing in the Pentagon at 200.

This morning, while huddling at the White House with his National Security Council, Bush warned the nation to be "keenly aware of the threats to our country" in the wake of the coordinated hijacking attacks that struck the Pentagon, obliterated the World Trade Center towers in New York, and downed four commercial airliners on Tuesday.

"The deliberate and deadly attacks, which were carried out yesterday against our country, were more than acts of terror. They were acts of war," Bush said. "This will require our country to unite in steadfast determination and resolve. Freedom and democracy are under attack."

The calamities could have hit the president even closer to home, administration officials revealed today. Attorney General John Ashcroft said the government "had specific and credible evidence that the White House and Air Force One were targets."

Bush spokesman Ari Fleischer said American Airlines Flight 77 was initially headed toward the White House.

As costs mounted for cleaning up the damage, hunting down the terrorists and heightening defense, Bush asked congressional leaders to approve an emergency request for funding.

"I am sending to Congress a request for emergency funding authority so that we are prepared to spend whatever it takes to rescue victims, to help the citizens of New York City and Washington, D.C., respond to this tragedy, and to protect our national security," Bush said this morning.

Lawmakers who just days ago were pinching pennies and bickering over the budget, quickly moved to draft an emergency spending package. Though the White House initially was hoping for a "blank check," Congress was moving toward a deal that would set some limits on spending and, as one congressional aide described it, "allow Congress to maintain constitutional prerogatives and the power of the purse."

But a spokesman for Senate Appropriations Committee Chairman Robert Byrd said reports that a $20 billion deal had been reached with the administration and House leaders were "premature."

"There have been good discussions all day long on how to proceed and what to do but there hasn't been anything finalized," Byrd spokesman Tom Gavin said. "I think they're gonna take a look at it in the morning with fresh eyes."

Pentagon Still Burning, But Workers at Desks

Back at the Pentagon, staffers had returned to their desks though large sections of building were cordoned off with crime scene tape. The building was evacuated briefly again today but quickly reoccupied after concern about one of the fires, still burning even after a full day of efforts to douse the flames, was filling halls of the five-sided building with smoke.

Secretary of State Colin Powell said 25 percent of the approximately 260 U.S. diplomatic missions around the world have been closed in response to the attacks. But at State Department headquarters and at other federal buildings that had been evacuated Tuesday, workers returned to their offices.

"The federal government and all our agencies are conducting business, but it is not business as usual," Bush said. "We are operating on heightened security alert."

Federal workers were on edge today. The Department of Agriculture was evacuated briefly due to security concerns. And employees at the Interior Department were herded into a basement cafeteria following a false report that an unauthorized plane had penetrated U.S. airspace.

‘The Darkest Day’

The White House had been evacuated and locked down Tuesday. But today, Bush was meeting there with congressional leaders and public tours had resumed.

On the other side of the city, Congress met under intense security, sending another signal to the world that terrorism has not crippled the United States. After closed-door briefings with top intelligence officials, lawmakers expressed concern that the bloodshed may not be over.

"This may not be over," Florida Sen. Bob Graham, chairman of the Senate Intelligence Committee, warned after the secret briefings. "We're in a yellow light situation."

Earlier, the Senate and House chaplains opened today's congressional session with emotional prayers for the injured, the killed and the nation. Lawmakers filed one by one to the podiums to express anger, sadness and determination to avenge the deaths of so many Americans.

"We must put ourselves in a war footing," Senate Republican Leader Trent Lott of Mississippi urged. "We must make up our minds we're going to fight this scourge of the world."

Rep. Ike Skelton, D-Mo., called Tuesday "the darkest day in American history."

"Pearl Harbor pales in comparison," Skelton said.

The Senate unanimously approved a resolution condemning the bombing, committing "to support increased resources in the war to eradicate terrorism" and backing the president's efforts — "in close consultation with the Congress" — to punish the perpetrators.

John McWethy, Dee Carden and Linda Douglass contributed to this report.