Nelson Mandela was given a tumultuous send-off last night at a sold-out rally in the Washington Convention Center, where he said American support of his campaign to abolish apartheid in South Africa has "created a firm bedrock upon which we can proudly walk."

"When we finally leave your shores, we shall do so fortified by the magnitude of your love, the greatness of your heart," said Mandela, who was to leave for Atlanta today. His U.S. visit ends Sunday.

He continued, "The message we shall take back home is that we came and found a truly great people, men and women of conscience . . . . Together with you, we can and indeed, must reach that future now. Let us march there by keeping the pressure on apartheid in South Africa. The hour of destiny has caught up with us."

The mostly black crowd of 19,000, some dressed in brightly colored African clothing, T-shirts with political messages or business attire, broke into a piercing cheer for about five minutes as Mandela took the podium shortly before 10 p.m. Some women cried, men hoisted young children on their shoulders for a better view. Thousands of fists pumped in the air.

On the floor and in the upper stands, hundreds of people did the South African toi-toi dance. Dozen of people pushed past security guards to rush forward and take pictures. Mandela smiled, waved at the crowd and returned the salute.

"I thought it was magnificent," said Ruth Sallay, an administrative officer for the federal government who lives in the District. "What I felt was he still has not given up hope that apartheid in South Africa is going to end." Sallay added that the one thing that struck her was that "Mandela felt that President Bush had given him a positive response to his quest {to continue the pressure on South Africa}. I am not so sure."

The rally capped a day in which Mandela crossed the line frequently between federal and local Washington. He was cheered when he addressed a joint session of Congress, and applauded by the unelected on the street.

Mandela's three days in the nation's capital were cast as a working statesman's visit. But yesterday he gave less official Washington a chance to glimpse him, to touch him, to let him hear his name shouted and sung.

Hundreds of people had waited outside the Convention Center in the hot summer sun -- some for as long as six hours -- before the doors opened.

Once inside the convention center, the crowd was entertained by the South African Chorus, which led them in singing South Africa's national anthem.

Bishop Smallwood E. Williams, pastor of the Bible Way Church in Shaw, gave the invocation, asking blessings on "the miracle of delivery that is in the making."

Many in the audience rose and applauded when Mayor Marion Barry and his wife, Effi, arrived on the dais. The mayor waved and smiled during the sustained ovation.

Earlier, Nelson and Winnie Mandela met privately with the Barrys. The Mandelas were given the keys to the city and were proclaimed honorary citizens of Washington, D.C., in perpetuity.

In a tribute to Mandela, Randall Robinson, executive director of the lobbying group TransAfrica, said, "We have serious questions to ask ourselves, serious commitments to make. How do we honor Nelson Mandela? Is it enough that we turn out by the thousands to cheer him?"

The audience responded with a resounding "No!"

"We must make a commitment to ourselves, to be active, to join the struggle, to make a democratic outcome the short-term reality in South Africa," Robinson said.

During his introduction of Mandela, Jesse L. Jackson told the former political prisoner: "You prove that truth crushed to the earth will rise again. And you made us better. You've made us appreciate life and love. You made us appreciate the goodness of a courageous and principled person. You are many things to many people. But to us, you are wind beneath our wings."

Nelson and Winnie Mandela sat on a raised dais before a black curtain on which "African National Congress" was written in large yellow letters.

Winnie Mandela addressed the audience after her husband's 15-minute speech, which was interrupted by applause about 20 times.

"Amandla, Amandla! {Power!}" she exclaimed. She wore a long red and black gown with a matching headdress. "Viva la ANC. Viva comrade {ANC President Oliver} Tambo. Viva comrade Mandela . . . .

"We need this for all the victims of apartheid . . . perhaps you have no idea what apartheid actually means in practical terms. It means we have men and women who are imprisoned by the South African government for their political actions," she said.

Interviewed on WUSA-TV (Channel 9) at the Convention Center, Barry said that earlier announcements that he would not attend the rally were based on uncertainties in his schedule and the time the rally would be held.

"Once I found out I could be here -- my wife is here too -- I couldn't miss this. I don't care what was going on."

Barry also was asked if he thought his attendance would in any way tarnish Mandela's appearance, because of Barry's trial on drug and perjury charges.

"I think the media, unfortunately, has tried to link all of this together," Barry said. "My situation is going to go on, regardless, and Nelson Mandela's triumphant entry into Washington is so big it overshadows anything that's going on.

"Marion Barry can't hurt anything. I have a long history here. And the people here -- if you could talk to them -- they'd tell you it would be unnatural for me not to be here."

Mandela, deputy president of the African National Congress, started his public day with a brisk 2 1/2-mile walk in the neighborhood around the Madison Hotel on 15th Street NW.

Just before 3 p.m., office workers filled the windows near the Madison Hotel, and a crowd four people deep erupted into applause when Mandela and his entourage walked across 15th Street to The Washington Post building where Mandela met with reporters and editors.

At mid-day, as he returned from addressing a joint session of Congress, Mandela's motorcade whisked past Freedom Plaza between 13th and 14th streets on Pennsylvania Avenue NW a little after noon. Even though he didn't stop -- as some had hoped he would -- an estimated 20,000 people gathered there for a rally stayed anyway and joined in a chant that consisted of reciting Mandela's name 27 times.

They posted themselves on office balconies, curbs and city benches along Pennsylvania Avenue and at Freedom Plaza. A large banner welcoming Mandela and his wife, Winnie, to Washington was strung on the front of the District Building across from Freedom Plaza.

Eric Peoples, 22, a securities sales representative, never saw Mandela's motorcade but said the rally was important because it gave the District's residents a chance to make a statement.

"It shows that a lot of people are fully behind him and it shows the government there is wide support for his cause," Peoples said. "I'm too young to have seen Martin Luther King or Malcolm. I feel that his cause is ours."

Staff writers Linda Wheeler, Patrice Gaines-Carter, Keith Harriston, Michele L. Norris, Marcia Slacum Greene, Avis Thomas-Lester, Athelia Knight, Retha Hill, Jenice Armstrong and Karlyn Barker contributed to this report.