South Korea's chief nuclear envoy departed Seoul for Washington DC on Wednesday morning, in a visit that will see him meet with U.S. counterparts and seek to come up with new ways to break through a now months-long impasse in talks with North Korea.Lee Do-hoon, whose formal title is Special Representative for Korean Peninsula Peace and Security Affairs, told reporters before his departure that he would be meeting with Deputy Secretary of State and Special Representative for North Korea Stephen Biegun during his visit.The two, he said, would seek to "think together about methods to overcome the