WASHINGTON — President Barack Obama opened a day of tributes today to former President John F. Kennedy by bestowing the Presidential Medal of Freedom on prominent Americans, 50 years after Kennedy was assassinated weeks short of the medal’s first award ceremony.

Obama presented the medal — the highest award the U.S. gives a civilian — to Oprah Winfrey, former President Bill Clinton, and leaders from sports, entertainment, science and public service. This was in the White House.

“Today, we salute fierce competitors who became true champions,” Obama said, pausing to speak in personal terms about each of the recipients and their contributions to society.

The ceremony marks the start of a day honoring Kennedy’s legacy two days before the nation pauses to remember the 50th anniversary of his assassination. Later, Obama will pay a visit to the eternal flame that marks John F. Kennedy’s gravesite.

He’ll be joined by first lady Michelle Obama and the Clintons at the ceremony at Arlington National Cemetery.

In the evening, Obama plans a speech on Kennedy’s legacy of service at a dinner at the Smithsonian’s National Museum of American History

Kennedy established the modern version of the medal, but was assassinated by Lee Harvey Oswald in Dallas on Nov. 22, 1963, two weeks before he planned to honor the inaugural group of recipients.