U.S. President Joe Biden will be the first sitting president to deliver a Sunday sermon at Martin Luther King Jr.'s church in Atlanta, as he marks a national holiday celebrating the civil rights leader, White House officials said on Friday. Biden will speak at Ebenezer Baptist Church on Sunday at the invitation of the church's pastor, Democratic Senator Raphael Warnock, on what would have been King's 94th birthday. King was killed at age 39 in 1968 by an avowed segregationist.