President Obama plans to deliver remarks at an Aug. 28 ceremony on the steps of the Lincoln Memorial commemorating the 50th anniversary of Martin Luther King, Jr.’s March on Washington.

As the first black president, Obama’s speech is particularly poignant — and likely will be the highlight of a week-long celebration of the march, which occurred on the same date in 1963 and climaxed in King’s “I Have a Dream” speech at the Lincoln Memorial.

The King Center, the nonprofit devoted to promoting MLK’s legacy of nonviolent protest in support of civil rights, and the 50th Anniversary Coalition are encouraging communities around the world to participate in a “Let Freedom Ring” bell-ringing ceremony at 3 p.m. EDT on Aug. 28, or at 3 p.m. in their respective time zones.

“My father concluded his great speech with a call to ‘let freedom ring,’ and that is a challenge we will meet with a magnificent display of brotherhood and sisterhood in symbolic bell-ringing at places of worship, schools and other venues where bells are available from coast to coast and from continent to continent,” said Bernice King, King’s daughter and CEO of the King Center.

The White House’s one-line announcement about Obama’s speech didn’t say whether it was scheduled to take place before or after the bell-ringing.