Updated

The impending inauguration of the nation's first black president is a huge step toward realizing Martin Luther King Jr.'s dream of racial equality, but there is still work to be done, King's nephew told a large crowd Monday at the church where the civil rights leader once preached.

Isaac Newton Farris, president of The King Center, told the jubilant crowd on what would have been King's 80th birthday that the election of Barack Obama was built on a foundation laid by King and was a "gigantic leap" toward the fulfillment King's dream. The sanctuary of Ebenezer Baptist Church was packed, with dozens of people left outside.

"There is definitely a spiritual connection between these two events," Farris told the mostly black congregation that erupted in applause at any mention of Obama's name.

But he cautioned the crowd that Obama's ascent to the nation's highest political office is not the final achievement of King's vision.

The Rev. Rick Warren — a Southern Baptist who opposes gay marriage — gave the King Day keynote address, urging the crowd to follow King's example of service and selflessness. He is also scheduled to give the invocation Tuesday at Obama's inauguration.

"Tomorrow when I pray the invocation for my friend, Dr. King and a whole host of witnesses will be shouting," Warren said. "Martin Luther King was a mighty tool in the hand of God. But God isn't through. Justice is a journey and we're getting further and further along."

Warren's appearance at the annual King holiday service was not without controversy. About 100 protesters gathered across the street, and there was an outburst from at least one critic before Warren addressed the audience.

Farris defended The King Center's choice of Warren as keynote speaker, saying he embodies many of the ideals espoused by King.

Farris said that as long as disparities persist in health care, education and economics, King's work remains undone.

"The dream was not about an individual or any race of people attaining power," Farris said. "It was a human dream."

King preached at Ebenezer Baptist Church from 1960 until his death in 1968.

Only one of King's three living children, Bernice, attended the Monday event. His sister, Christine King Farris, led the ceremony.

King's son Martin Luther King III was in Washington already and his other son Dexter King — who lives in California — did not attend. Their other sister, Yolanda, died in 2007.