Prime Minister Manmohan Singh on Sunday met US President Barack Obama and is understood to have discussed nuclear security, India’s concerns over American military aid to Pakistan and the volatile situation in Afghanistan. Obama walked down across the White House to meet 77-year-old Singh at the Blair House, the US President’s official guest house, their second meeting in nearly five months. Singh and Obama had last met at the White House on November 24, 2009, during the former’s State Visit.