Filed at 11:14 a.m. ET

WASHINGTON (AP) -- President Bush on Wednesday condemned terrorist attacks in New York and Washington as ``acts of war,'' and said he would ask Congress for money to help in the recovery and protect the nation's security.

``This will be a monumental struggle of good versus evil. But good will prevail,'' the president said. He said the nation was prepared to spend ``whatever it takes.''

Bush spoke as administration officials said evidence in Tuesday's fearsome attacks pointed to suspected terrorist Osama bin Laden, harbored in Afghanistan. And while Secretary of State Colin Powell suggested earlier in the day that no military response was imminent, Bush said, ``We will rally the world'' in the war on terrorism, fought now on American soil.

Congress returned to the Capitol and federal agencies reopened their doors for the first time since Tuesday's parallel attacks on the World Trade Center in New York and the Pentagon across the Potomac River from the nation's capital.

Bush, in the Oval Office shortly after sunrise, invited senior lawmakers to the White House for a national display of unity.

His spokesman, Ari Fleischer, spoke words meant to soothe. ``We believe the perpetrators have executed their plan and therefore the risks are significantly reduced,'' he said.

A mile or so from where he spoke, search and rescue teams worked in the remains of the portion of the Pentagon that collapsed on Tuesday, hit by a hijacked jetliner. Officials said they doubted they would find any additional survivors, and said the number of deaths could reach into the hundreds.

That would pale in comparison to the carnage in New York, where two more hijacked planes were flown into the twin towers of the World Trade Center. The buildings collapsed, with thousands feared lost.

In a day-after scare, employees at the Agriculture Department's main building along the National Mall were evacuated about 9 a.m. but were allowed back in an hour later. Reports of unidentified aircraft in Canadian airspace prompted the evacuation, Chris Gomez, deputy director of the department's office of operations, told employees.

Another U.S. official, speaking on condition of anonymity, said there were three unidentified aircraft over Canada and the Canadian Air Force was tracking them, but added that the United States was not greatly concerned.

Making the rounds of the morning television programs, Powell reinforced Bush's Tuesday night pledge that the attacks would be avenged. Administration officials say their early investigation has pointed to suspected terrorist Osama bin Laden, but the secretary of state made it sound like no military response was imminent.

He said the administration was ``far from selecting any particular targets for retaliation

``We have to build a case first,'' he said.

Congress convened with prayers and expressions of resolve that the perpetrators would be found and punished. ``The world should know that members of both parties and both houses stand united in this,'' said Senate Majority Leader Tom Daschle, D-S.D.

Powell said Americans have made the judgment: ``We are at war and they want a comprehensive response. They want us to act as if we are at war and we're going to do that -- diplomatically and militarily.''

The State Department, which closed after the attacks, opened again. Powell said one-quarter of U.S. embassies were still closed as a precaution.

The U.S. air space, closed to commercial traffic for the first time, was expected to reopen at noon EDT, said Dorr, speaking for the FAA. He said it would take time for airlines to get back to normal schedules, with so many planes diverted to wrong locations.

He suggested passengers who would normally go the airport an hour before a flight should go two hours in advance.

At the White House, Bush and his wife, Laura, were asking Americans to donate blood, spokesman Gordon Johndroe said. Bush was also meeting his national security team.

Pentagon workers were able to enter sections of their building but nearly half the structure had no power and some employees were asked not to show up. Among those at their desks were Defense Secretary Donald H. Rumsfeld and Army Gen. Henry H. Shelton, chairman of the Joint Chiefs.

Bush, addressing the nation Tuesday night, condemned the ``acts of mass murder.'' The death toll in New York was unknown but thought to be surely in the thousands; the Arlington County, Va., fire department estimated 100 to 800 people died in the Pentagon attack.

``Our military is powerful, and it's prepared,'' a somber Bush said in his Oval Office address.

Bush said in his televised address, ``We will make no distinction between the terrorists who committed these acts and those who harbor them.''

Streets around the White House were reopened overnight, but the capital city remained under close watch as Wednesday dawned with more police on patrol than usual. They were supplemented by 30 to 50 National Guardsmen stationed -- in pairs with a Humvee -- at more than a dozen street corners in the main business section.

Powell said he knew of no indications that terrorists would immediately follow up on their assault. There was ``nothing to suggest that there is something waiting to happen today.''

And he said it was realistic to expect that Americans could track down the terrorists. ``Sometimes it takes a few weeks, sometimes it takes years. But we won't give up. We will find them and they will be dealt with.''

Lawmakers also arranged to convene to condemn the terrorism -- a day after the Capitol was evacuated and congressional leaders were hastily ferried to an underground bunker 75 miles away.

``The Pentagon is functioning,'' a defiant Rumsfeld said Tuesday night, despite the crash that sent a bright orange fireball skyward and caused the collapse of a section of one of the massive building's five sides.

Sen. Orrin Hatch, R-Utah, said U.S. intelligence intercepted communications between bin Laden supporters discussing the attacks.

The suspected fugitive terrorist has been sheltered in Afghanistan, but that nation's hardline Taliban rulers rejected suggestions he was to blame.

Officials declined repeatedly Tuesday night to estimate the number of injured or dead in the attacks. Bush himself referred to ``thousands of lives'' being ended and Sen. Hillary Clinton, D-N.Y., said ``I don't think we've had an inkling of the devastation'' in downtown Manhattan.

Amid the devastation, Bush offered reassuring words. ``These acts of mass murder were intended to frighten our nation into chaos and retreat. But they have failed,'' he said. Our country is strong. A great people has been moved to defend a great nation.''