Washington showed the first signs of becoming a wartime capital yesterday, as security dramatically increased at airports and federal buildings, protests spilled into neighborhood streets and residents realized that they live in a city that could be a prime terrorist target.

As the United States approached the brink of war with Iraq, downtown workers nervously eyed the White House, where extra guards were on alert. Airport skycaps worried there will be layoffs if bags can no longer be checked at the curb, and many government employees were forced to show their rarely used identification cards when they arrived at the office.

Doris Landsdowne, a dental hygienist who works blocks from the White House, thought about switching jobs to a safer location and told her 12-year-old son he probably won't travel to Paris with other Fairfax County students this spring.

"This is not like Vietnam, when the war was confined. It was horrible, but you didn't feel threatened at home like you do now," Landsdowne said. "I feel uncertain and scared. Every single patient I've had today has said that these are sad times."

In interviews with dozens of people across the Washington area, from downtown lunch counters and the national monuments to suburban homes and airports, men and women, young and old, said the worsening crisis in the Persian Gulf was directly affecting, and often altering, their lives. Many were glued to radios and televisions, listening for developments.

Debra Malik, a budget assistant for the Resolution Trust Corp. at 17th and H streets, was stopped at the door of her office while her picture identification was carefully examined, a precaution she has never seen before. "I'm very nervous. I don't think it's safe around here anymore," she said.

At National Airport, Eastern Airlines ticket agent Simone Pierson's heart pounded as a briefcase was left unattended in front of her counter.

"It was really scary," said Pierson, who, like all airport employees, was instructed to keep a sharp eye out for abandoned packages and unusual passengers: those holding one-way tickets, in a great hurry or without any luggage. When Pierson spotted the abandoned briefcase, she said, "My heart just went, 'Oh, my God.' I find myself not standing next to trash cans because that's a place where they might put a bomb."

Tourist Susan Galeano wanted to get out of town and back home to Hunt Springs, S.D., quickly.

"You can feel the tenseness in this town," said Galeano, a nurse at a Veterans Hospital. "I work in the detox and psych unit there, and we have a mess from the Vietnam War. This is horrifying. I wish I was going home, because after tomorrow, you don't know what is going to happen. I'd like to get out of Washington."

Shirley Furbush, a District advocate for the homeless whose son, Damon, 28, is an Army transport specialist in Saudi Arabia, was headed for a White House vigil yesterday but changed her mind, out of fear.

"I was going to stand by the fence even though I believe Bush has made up his mind" to attack Iraq, Furbush said. "But I'm too worried about foreign terrorists. I do believe terrorists will attack here."

Furbush, who has been distributing shoes to homeless people on street corners, said she was too upset to finish passing out the 100 Nike sneakers she had left.

"I found myself in a room crying today. . . . Think of all the lives affected. Who can stay calm?"

Malik, the budget assistant, who lives in Temple Hills, said her daughter turns 19 tomorrow. "But how can we celebrate and be happy right now?" she said. "I've got to think about myself and my daughter getting hit by a terrorist attack, about my nephews coming back {from the Persian Gulf} alive or being taken prisoners of war, about what's going to happen to the whole country."

Security was visibly tighter at National Airport yesterday, where armed police officers and walkie-talkie-toting security officials patroled the corridors.

"Our state of awareness increased measurably," said Metropolitan Washington Airports Authority spokesman David Hess.

Skycaps said they have been told that if war breaks out, they will no longer be able to check luggage at curbside. "We'll just be hauling {bags}, which means that a lot of us will be unemployed," said Diana Garrett. "That's more of a scare than the war."

At Dulles International Airport, intensive weapon searches were conducted at security checkpoints.

Federal Aviation Administration spokesman Fred Farrar said his agency is "working closely with the airlines and airport authorities to ensure a heightened level of security for air travelers."

Discussions about the possibility of terrorism have been held in recent days by Metro transit officials, but they have no plans to close train stations, such as those serving the area's tourist destinations, said spokeswoman Beverly Silverberg.

The regional transit agency has a continuing program with local and federal law enforcement officials to deal with terrorist threats, and it conducts periodic drills, she said.

Many local universities and high schools canceled or put on hold programs involving study abroad because of State Department travel advisories. T.C. Williams High School in Alexandria canceled its Israeli exchange program. Georgetown University scratched programs in Israel and Egypt. And two more American University students withdrew yesterday from European study abroad programs, according to Shaik Ismail, program director.

Anti-war protests, prayer vigils and peace marches were staged throughout the city.

In the largest demonstration, hundreds of people from several religious denominations marched in a candlelight procession through the city from the Washington Cathedral to the White House.

Staff writers Steve Bates, Paul Duggan, Kent Jenkins Jr., Brooke A. Masters and Steve Twomey contributed to this report.