Updated at 9.29pm

PRESIDENT BARACK OBAMA has led his nation in homage to Martin Luther King Jr, in a speech at the spot where the civil rights icon voiced a soaring dream of equality 50 years ago.

In a moment of high symbolism, America’s first black president reflected on King’s legacy and the long march to fulfill the hopes of the “I have a dream” speech, delivered from the steps of the Lincoln Memorial in Washington.

Otherwise known as The Great March on Washington, the rally on 28 August 1963 attracted between 200,000 and 300,000, protesting the ongoing struggle the black population of the United States faced to attain full realisation of their civil rights.

Speaking ahead of Obama, former US President Bill Clinton used his speech to call for greater racial harmony. He said: “In the shadow of Lincoln’s statue, the burning memory of the fact that he gave his life to preserve the Union and end slavery, Martin Luther King urged his crowd not to drink from the cup of bitterness, but to reach across the racial divide because, he said, we cannot walk alone.”

Opening his speech, President Obama paid tribute Dr King, saying he “gave mighty voice to the quiet hopes of millions” and that his “words belong to the ages – their power and prophecy unmatched in our time”.

Obama said King had “offered salvation to oppressed and oppressors”.

Ordinary people

He then spoke of the “ordinary people whose names never appeared in the history books” who travelled from all over America to Washington fifty years ago.

He said they had saved to undertake the journey from where they lived in “towns where they couldn’t vote” or “cities where their votes didn’t matter”.

“They had seen loved ones beaten and children fire-hosed, and they had every reason to lash out in anger.

Yet they chose a different path

He said that “in the face of hatred, they prayed for their tormentors”.

“Willingly they went to jail – the cells swelling from the sounds of freedoms songs.”

“That was the spirit they brought here that day,” he said. “That was the spirit they carried with them like a torch.”

Doors of opportunity

Obama said that “because they marched, doors of opportunity and education were swung open” and that “city councils changed, state legislatures changed, Congress changed, and eventually, the White House changed”.

He said that because of the events of fifty years ago, American society had become a fairer place for all minorities, and that “the entire world drew strength from that example”.

[The Rev. Martin Luther King Jr. waves to the crowd at the Lincoln Memorial on Aug. 28, 1963. AP/Press Association Images]

Later, he said that in some ways the significance of securing of civil rights and voting rights “may have obscured a second goal of the march”.

He said that the men and women who gathered fifty years ago were “not there in search of some abstract ordeal” but had also been seeking “jobs and economic opportunity”.

“Dr King explained that the goals of African Americans were identical to those of all Americans,” he said.

Fallen short

Obama said that it was in pursuit of that “second dimension of economic opportunity” that America had fallen short.

He said that in the intervening years upward mobility had become harder, and that “we must remind ourselves” of the goal of admitting “all people who work hard into the ranks of middle class life”.

He said that battle remained the nation’s “great unfinished business”.

Crowds were already gathering on the National Mall in Washington this morning four hours before Obama was due to speak. A several thousand strong crowd also marched through the streets of the capital.

ABC News, quoting law enforcement sources, put the crowd numbers at “over 20,000″ in advance of the President’s address.