US President Barack Obama and First Lady Michelle Obama have paid their respects at the grave of former President John F Kennedy to mark the 50th anniversary of his assassination.
They were joined by former President Bill Clinton and his wife Hillary Clinton.
A wreath was laid at the grave site in Arlington National Cemetery.
Surviving members of the Kennedy family were also present.
On Friday the nation will remember the shooting which happened in Dallas in 1963.
Former President Bill Clinton and chat show host Oprah Winfrey were among the recipients of the Presidential Medal of Freedom award today.
President Obama presented the award to 16 prominent Americans during a ceremony at the White House.
The award, regarded as the nation's highest civilian decoration, was established by John F Kennedy less than a year before his death.
Obama said the ceremony was one his favourite events of the year, and claimed this year's ceremony was "just a little more special" as it is 50 years since President Kennedy created the award.
President Obama will be joined by Bill and Hilary Clinton at a ceremony at Kennedy's grave site later on tonight as the nation prepares to honour the President's legacy on the 50th anniversary of his assassination.
Former US Secretary of State Hillary Clinton has been presented with this year's Chatham House Prize in recognition of her contribution to international diplomacy.
The central London institute also commended Mrs Clinton for her work towards gender equality and opportunities for women and girls.
The annual prize is awarded at Banqueting House in Whitehall to the statesperson deemed to have made the greatest contribution to improving international relations in the previous year.
Bill Clinton has responded to Bono's impersonation attempt with his own impression of the U2 singer.
Appearing on Piers Morgan's CNN talk show, Clinton pulled on a pair of dark glasses before trying out an Irish accent.
Earlier this week Bono delighted the crowd at a Clinton Global Initiative event with a striking impression of the former US president.
U2 singer Bono has been showing off his best American drawl as he impersonated for Bill Clinton.
As he waited for the former US president on stage at the Clinton Global Initiative in New York, Bono began a striking impersonation of Mr Clinton.
To the obvious delight of the audience the U2 frontman described how Clinton "thought he was one his roadies" the first time they met before listing their humanitarian achievements.
When Mr Clinton did arrive the Irish singer leapt back in to his own seat as the former president said he "must be really easy to make fun of."
Bono filled in for Bill Clinton at a meeting of heads of state and business leaders - by jumping into the former US President's chair and doing an impression of him.
The U2 star was on the panel of a meeting of the Clinton Global Initiative in New York, and took over when the politician was late arriving on stage.
Former US President Bill Clinton has tweeted this photo of himself with his predecessor George Bush Snr.
The pair have lunch together every year in the state of Maine, where Mr Bush owns a large estate on the coast.
Mr Clinton drew attention to his host's "western cactus" themed socks, of which he said he was "envious".
Former US President Bill Clinton may be better known for playing the saxophone than his singing, but thanks to YouTube user baracksdubs that could be a thing of the past.
Thanks to some clever editing, Clinton has taken on one of the sounds of the summer, Robin Thicke's controversial hit Blurred Lines.
It is not the first time baracksdubs has got creative with a President and a chart topper - previous clips include Barack Obama singing Daft Punk's Get Lucky, LMFAO's Sexy and I Know It and Carly Rae Jepson's Call Me Maybe.
President Barack Obama is to bestow America's highest civilian honour on Oprah Winfrey and former president Bill Clinton.
The pair will receive the Presidential Medal of Freedom at a ceremony at the White House later this year.
The medal is presented to individuals who have made "especially meritorious contributions to the security or national interests of the United States, to world peace, or to cultural or other significant public or private endeavours."
Ms Winfrey and Mr Clinton will join 14 other recipients, including activist Gloria Steinem and former senator Richard Lugar. Also being honoured is Ben Bradlee, the editor who oversaw Washington Post coverage of Watergate.
Former senator Daniel Inouye of Hawaii and Sally Ride, the first woman astronaut in space, will receive the medals posthumously.
President John F Kennedy created the medal of freedom in an executive order signed 50 years ago. The White House says more than 500 people have been presented with the honour to date.