Sarah Montague talks to David Sanger, Chief Washington Correspondent of the New York Times. In his new book, The Inheritance, he looks at the immense problems which have developed around the world while America trained its attention on Iraq. What do the world's leaders make of the new US President, now they've had a chance to meet him? It is the first time Barack Obama has met the presidents of Russian, China and India. Quite apart from talk of saving the world's economy, there are huge challenges ahead.