Obama to give personal reflections on Martin Luther King Jr. at 50-year anniversary of March on Washington

Fifty years after Martin Luther King Jr. shared with a divided nation his “dream” of racial equality, America’s first black president will mark the anniversary – and the progress made since the 1963 March on Washington -- on the steps of the Lincoln Memorial.

The president will be joined Wednesday for the “Let Freedom Ring” ceremony by a host of civil rights leaders, as well as past presidents and members of the King family. Obama will speak roughly 50 years to the minute since King delivered his famous “I Have a Dream” speech.

He is expected to offer his personal reflections on the civil rights movement, King's speech, the progress achieved in the past 50 years and the challenges that demand attention from the next generation.

The ceremony will also feature musical and dance performances, and notable guests from Oprah Winfrey to U.N. Secretary General Ban Ki Moon via video. It will be emceed by Soledad O’Brien and Hill Harper.

Former Presidents Jimmy Carter and Bill Clinton will also attend. Former President George W. Bush, who was invited but is still recovering from a heart procedure and will not attend, said in a written statement that “our country has come a long way since that bright afternoon 50 years ago; yet our journey to justice is not complete.”

In a radio interview Tuesday with Tom Joyner and co-host Sybil Wilkes of the Tom Joyner Morning Show, Obama said he imagines that King "would be amazed in many ways about the progress that we've made." He listed advances such as equal rights before the law, an accessible judicial system, thousands of African-American elected officials, African-American CEOs and the doors that the civil rights movement opened for Latinos, women and gays.

"When you are talking about Dr. King's speech at the March on Washington, you're talking about one of the maybe five greatest speeches in American history," Obama said.  "And the words that he spoke at that particular moment, with so much at stake, and the way in which he captured the hopes and dreams of an entire generation I think is unmatched."

In tribute, Obama keeps a bust of King in the Oval Office and a framed copy of the program from that historic day when 250,000 people gathered for the March on Washington for Jobs and Freedom.

First Lady Michelle Obama will accompany her husband. On Tuesday night, the First Lady attended a screening of a documentary about civil rights leader Whitney Young, who was one of the organizers of the march.

After the screening, Mrs. Obama urged the audience that included middle and high school students from Washington, D.C., and Loudon County, Va., to become "agents of change" like Young, calling him one of the "unsung heroes" of the civil rights movement.

On Saturday, tens of thousands of people marched to the Martin Luther King Jr. Memorial and down the National Mall to commemorate the anniversary of the speech.

The event was in homage to a generation of activists who endured fire hoses, police abuse and indignities to demand equality for African Americans, and to the thousands who marched in the peaceful demonstration on Aug. 28, 1963.

An estimated 200,000-300,000 people participated in the March on Washington to demand greater civil rights for African Americans.  In his famous speech, King called for the end of racial injustice in the U.S.

The march and its effects are credited with helping pass the Civil Rights Act in 1964 and the Voting Rights Act in 1965, both of which insured equal rights for all U.S. citizens.

The Associated Press contributed to this report