Tape sheds light on John F Kennedy's call to Martin Luther King's wife

As Americans reflect on the legacy of Martin Luther King Jnr, an audiotape of an interview with the civil rights leader discovered in a Tennessee attic shed new light on a famous phone call John F. Kennedy made to King's wife more than 50 years ago.

A copy of the original recording was to be played for visitors at the National Civil Rights Museum in Memphis, in the southern US state, at a "King Day" event yesterday.

Historians generally agree that Kennedy's call to Coretta Scott King expressing concern over her husband's arrest in October 1960 - and his brother Robert Kennedy's work behind the scenes to get King released - helped Kennedy win the White House a month later.

King himself, while appreciative, wasn't as quick to credit the Kennedys alone with getting him out of jail, according to a previously unreleased portion of the interview with the civil rights leader days after Kennedy's election.

"The Kennedy family did have some part ... in the release," King says in the recording, which was discovered in 2012. "But I must make it clear that many other forces worked to bring it about also."

King was arrested a few weeks before the election at a sit-in in Atlanta, in the state of Georgia. Charges were dropped, but King was held for allegedly violating probation for an earlier traffic offence and transferred to the Georgia State Prison.

The Kennedys' intervention won the support of black voters, who helped give Kennedy the edge in several key states.