WASHINGTON - Fifty years ago Thursday, US President John F. Kennedy told the world that "the torch had been passed to a new generation of Americans" whom he challenged to "ask not what your country can do for you -- ask what you can do for your country."

The Harvard Glee Club takes a bow after singing at a kickoff concert for a celebration of the 50th anniversary of late US President John F. Kennedy's inauguration, at the Kennedy Center concert hall in Washington, Jan 20, 2011. [Photo/Agencies]

Caroline Kennedy told The Associated Press that she has been thinking over her father's oft-quoted inaugural speech on Jan 20, 1961, when he proclaimed that Americans "shall pay any price, bear any burden, meet any hardship, support any friend, oppose any foe, to assure the survival and the success of liberty."

"I think he really expanded and redefined our idea of what it means to be a citizen -- that everybody has something to contribute and everybody has something to give back to this country that's given us so much," Caroline Kennedy said. "It's not just an obligation, but it's really a rewarding experience and really a belief in government and politics as a noble profession."

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Kennedy joined members of her father's administration, civil rights activists, astronaut Buzz Aldrin and members of the first class of the Peace Corps -- which JFK established -- to mark the 35th president's legacy at the Capitol on Thursday.

About 100 members of the Kennedy family gathered at the Kennedy Center for the Performing Arts. The center on the bank of the Potomac River stands as a living tribute to Kennedy, whose White House embraced the arts.

It opened three weeks of performances that will recreate moments from those "Camelot" days.

President Barack Obama in opening the concert Thursday night paid tribute to the "unfinished life" of JFK and said his inauguration and his accompanying call for Americans to serve their country still "inspires us and lights our way."

Obama, who wasn't born until later in 1961, hailed Kennedy for leading a "volatile America in this tinderbox of a world," with a steady hand, "defusing the most perilous crisis since the Cold War without firing a single shot." He also noted Kennedy's work to help blacks attend their choice of college, launch the Peace Corps of goodwill ambassadors around the world and set America's sights on landing on the moon.

Though the country faces different challenges today, Obama said, "we cannot forget we are the heirs of this president who showed us what was possible. Because of that vision, I can stand here today as president of the United States."

Earlier, speaking at a ceremony in the Capitol's rotunda, Vice President Joe Biden said Kennedy's cause was to bring America back "to what it should be."

"His call to service literally, not figuratively, still resounds from generation to generation," Biden said.

The celebrations come as the Kennedy power in Washington has faded. For the first time in 63 years no one with the Kennedy name is serving in elected office. Patrick Kennedy of Rhode Island left the US House this month.

Caroline Kennedy said she wouldn't be surprised if someone in her family returned to national politics -- but that it probably wouldn't be her. She flirted with a 2008 Senate bid in New York but bowed out.

Instead, she is announcing a new "Ask Not" public service campaign with Jimmy Fallon aimed at youth as part of a series of events to reconnect the Kennedy legacy with a new generation. The spots featuring Fallon will air on Viacom, Comcast and CBS television channels to promote the new website JFK50.org.

Caroline Kennedy hasn't given up on politics, though. While many young people place a high value on volunteering and community service, she said politics has somehow become less attractive to them. And she wants to change that.

"We hope they'll see that it's a continuum and you need the political process to solve these problems that they are already working on so hard," she said.