President Obama urged the nation Sunday to celebrate the dedication of the memorial to slain civil rights leader Martin Luther King Jr. by continuing to press for the goals and hopes of the “black preacher with no official rank or title who somehow gave voice to our deepest dreams” and helped make the nation “more perfect.”

In a speech that at times seemed to link King’s own struggles for civil rights with Obama’s political struggles during the economic downturn, the president said the nation was still encountering many of the same challenges that King saw when he made his “I Have a Dream” speech that helped to galvanize the civil rights movement in 1963.

Obama told more than 10,000 spectators and dignitaries who helped unveil the King monument on the national Mall that in many communities little has changed.

“In too many troubled neighborhoods across the county, the conditions of our poorest citizens appear little changed from what existed 50 year ago,” he said.

“There are neighborhoods with underfunded schools and broken down slums, inadequate health care . . .violence. Our work is not done.”

“So on this day when we celebrate a man and a movement that did so much for our country let us draw strength from those earlier struggles,” Obama said.

Making changes that might rock the status quo, as King and other civil rights leaders attempted with civil disobedience, sit-ins, and marches, is no easy task, the president said. And that lesson, he said, could be applied today.

“It is right to remind ourselves that such progress did not come easily. . . it came from the smack of billyclubs, and blasts of fire hoses . . . the nights of bomb threats. For every victory in the height of the civil rights movement there were setbacks, there were defeats,” Obama said. But King and other leaders, as well as thousands of foot soldiers in the civil rights movement, persisted, and ultimately prevailed by helping secure passage of key civil rights and voting rights legislation.

“Let us draw strength from those earlier struggles,” said Obama, adding that the nation today is “more fair and more free and more just” than the one King addressed.

King was attacked for his activism, labeled a communist and accused of lacking patriotism, but he also encouraged reconciliation among those who disagreed with one another, a path that Obama said the nation should follow today.

“I know we will overcome. I know there are better days ahead,” Obama said to applause. “Let us keep striving, let us keep struggling, let us keep climbing to that promised land of a nation and a world that is more fair and more just.”

As Obama began to speak, the crowd drowned him out by shouting “four more years,” but then fell quiet. Many held their children on their shoulders and their cellphones aloft to capture Obama’s remarks on video.

Obama, who was six when King was assassinated in 1968, said King deserved a place on the national Mall because “he had faith in us. . . and that is why he belongs on this Mall: Because he saw what we might become.”

Hugh Blackwell, 32, of Reston, a salesman for an electrical supply company, said after Obama’s speech that he was struck by the quiet scene that played out over the big screen televisions when the president toured the memorial with the first lady and their children Sasha and Malia.

Blackwell said the moment was extremely symbolic and showed the progress since King’s death.

“It was America as it should be,” Blackwell said.

Staff writers Theola Labbe-DeBose and Carol Morello contributed to this report.