South Korea's top nuclear envoy Wi Sung-lac is to visit the United States next Monday to discuss the six-way nuclear talks and the sinking of a South Korean warship. <br/><br/>The country's foreign ministry said Wi Sung-lac is scheduled to visit Washington on his way back from the G20 meetings in Canada. He is expected to meet with senior U.S. officials including Deputy Secretary of State James Steinberg and U.S. chief nuclear envoy Stephen Bosworth.<br/>