Driven by new evidence that North Korea may have begun selling nuclear materials around the world, President Bush sent an emissary last week to see President Hu Jintao of China and urge him to intensify diplomatic pressure on the North to give up its weapons program, according to senior American and Asian officials. The emissary, Michael Green, delivered a letter from Mr. Bush to Mr. Hu that, in the words of one American official, “was written to underscore the greatly heightened urgency” of the problem. Full Story