US President Barack Obama has dedicated a new memorial to the assassinated civil rights leader, Martin Luther King, at a ceremony in Washington. Addressing the crowd, Mr Obama said that Dr King was now among the founders of the American nation. The 30 ft (9m) granite statue lies near the spot where Dr King delivered his famous "I have a dream" speech in 1963. The ceremony had been due to take place in August but was postponed due to Hurricane Irene. 'Draw strength' President Obama toured the monument with his wife, Michelle, and his two daughters. Speaking to an audience of tens of thousands, he said Americans were right to celebrate Dr King's dream, and vision of unity. "On this day, in which we celebrate a man and a movement that did so much for this country, let us draw strength from those earlier struggles," he told the crowd on the National Mall in the US capital. "When met with hardship, when confronting disappointment, Dr. King refused to accept what he called the 'is-ness' of today. He kept pushing for the 'ought-ness' of tomorrow," Mr Obama said. "In this place, he will stand for all time, among monuments to those who fathered this nation and those who defended it." The statue is situated between the memorials for Presidents Thomas Jefferson and Abraham Lincoln. Born in Atlanta, Georgia, in 1929, Martin Luther King was a clergyman and leading figure in the US civil rights movement. He was assassinated in 1968 during a visit to Memphis, Tennessee, aged 39.