Barack Obama called Sunday for a new spirit of sacrifice to overcome war and economic crisis, as a constellation of stars kicked off a three-day inauguration party for America's first black president. Standing in the shadow of the Lincoln Memorial, dedicated to the slain president who brought the United States intact through the Civil War and abolished slavery, Obama gave a somber assessment of the perils ahead. “In the course of our history, only a handful of generations have been asked to confront challenges as serious as the ones we face right now. Our nation is at war. Our economy is in crisis,” he said. “I won't pretend that meeting any one of these challenges will be easy. It will take more than a month or a year, and it will likely take many,” Obama said. “But never forget that the true character of our nation is revealed not during times of comfort and ease, but by the right we do when the moment is hard. “I ask you to help reveal that character once more, and together, we can carry forward as one nation, and one people, the legacy of our forefathers that we celebrate today.” U2, Bruce Springsteen and Stevie Wonder -- whose songs were totemic anthems of Obama's barnstorming rise to power -- headlined a concert for a sea of people standing in arctic cold in front of Abraham Lincoln's memorial. The hundreds of thousands attending were the advance guard of an inaugural crowd expected to number millions, as an unprecedented security operation began with police and army reservists taking up position across the US capital. Hollywood royalty including Tom Hanks, Jamie Foxx and Denzel Washington recited historical passages interspersed with the all-star musical lineup, to mark the formal countdown to Tuesday's momentous inauguration on Capitol Hill. In advance of the afternoon party, Obama struck a more somber note as he joined vice president-elect Joseph Biden in laying a wreath at the Tomb of the Unknown Soldier in Arlington Cemetery. Dressed in black winter coats to guard against the freezing temperatures, Obama and Biden held their hands over their hearts as “Taps,” the US military's haunting lament to the fallen, was played by a lone bugler. Obama and his wife Michelle then climbed into the incoming president's new armored Cadillac with a blue license plate reading “44” – his numerical position as the newest commander-in
