US President Barack Obama lays a wreath at the 9/11 Memorial in New York on May 5, 2011. Obama was Thursday braced for a “bittersweet” visit to Ground Zero after the killing of Osama bin Laden, but felt it was important to go to offer “closure” to Americans. AFP PHOTO/Jewel Samad (Photo credit should read JEWEL SAMAD/AFP/Getty Images)