In the largest anti-war demonstration since the Persian Gulf crisis began, thousands of protesters gathered at the Washington Cathedral last night and marched in a candlelight procession to the White House, chanting "Peace Now" and singing songs from the Vietnam War era.

Secret Service officials estimated that 5,000 demonstrators filled the sidewalk and part of Pennsylvania Avenue NW in front of the White House.

Cathedral officials provided a similar estimate for the crowd that jammed the church for an hour-long multidenominational prayer vigil.

After the marchers left the cathedral about 9 p.m., traffic came to a standstill along the procession route.

Some motorists abandoned their cars, others honked their horns in support, and some yelled at the demonstrators.

The protest capped a day of demonstrations large and small throughout the capital, as the United Nations deadline for Iraq's withdrawal from Kuwait drew near. Some anti-war protesters delivered "flowers for peace," while others paraded a flag-draped coffin and held smaller candlelight vigils around the city.

U.S. Park Police officials said seven people were arrested in yesterday's protests.

"Our numbers here tonight indicate our fear and our pain and our grief and our fragile hopes," the Rev. Jim Wallis, editor of Sojourners magazine, told the crowd at the cathedral.

They listened as the Rev. Henri Nouwen of the L'Arche-Daybreak Community said they had gathered to pray for those "afraid to fight, afraid to be killed and afraid to kill . . . and afraid of the uncertainty of the future."

About the same time, some 500 people gathered at another candlelight prayer vigil in front of the Lincoln Memorial. That event drew Del. Eleanor Holmes Norton, the District's nonvoting representative in Congress, and Effi Barry, the wife of former mayor Marion Barry.

"Let us pray that there is divine intervention," Barry told the crowd.

The evening crowds in front of the White House were so large that protesters pressed tightly against the fences as they watched the building, apparently waiting for some sign of acknowledgment from the lighted windows. The only visible face was that of a law enforcement officer in a doorway.

"What do we want?" the crowd chanted over and over again. "Peace now," came the refrain.

Before reaching the White House, the marchers stopped at the Iraqi Embassy at 18th and P streets NW, where another group of demonstrators had unfurled a long gray sheet fashioned after the Vietnam War Memorial.

On it, they said, were the names of Americans who had died in the Persian Gulf since August.

Among those marching were families, students and young men who described themselves as being of draft age. "I'm scared as hell about the whole situation," said 17-year-old Jeremi Duru, a student at Montgomery Blair High School in Silver Spring.

Bill Welch, 46, who is partly paralyzed on his right side from a stroke he suffered several years ago, marched the several mile procession to the White House with the aid of a cane.

"Life is full of hard luck," Welch said of his disability. "But you could say every {U.S. military} person in Saudi Arabia has had hard luck."

After the White House gathering, about 70 demonstrators went to the nearby Metropolitan AME Church on M Street NW to hold an all-night vigil.

Earlier in the day, other protesters gathered at the Iraqi Embassy and the White House.

Activist Dick Gregory, who was arrested three times, led a prayer vigil and delivered letters beseeching Iraqi President Saddam Hussein and President Bush to avoid "unleashing the dogs of war."

A group representing Hawaiian protesters presented embassy and White House officials with a peace offering: 100 long-stemmed flowers.

The protests were a continuation of the expression of sentiments building across the city as war has drawn closer.

Activists expect the anti-war effort to grow with the passing of the deadline at midnight tonight, with demonstrations planned in Washington for the next two Saturdays.

D.C. Mayor Sharon Pratt Dixon told a group of federal workers that she opposed the congressional resolution granting President Bush authority to wage war.

Citing the disproportionate number of black troops in Saudi Arabia, Dixon said it was ironic that the country this week marks the birth of the Rev. Martin Luther King Jr.

Nation of Islam leader Louis Farrakhan, returned recently from a visit to Iraq for a Moslem conference, urged Bush to "think sanely, think wisely" before going to war.

Among those arrested at the White House yesterday were Carol Fenelley, of the Community for Creative Non-Violence, and peace activist Daniel Ellsberg.

Staff writers Ruben Castaneda, Mary Ann French and Laura Sessions Stepp contributed to this report.