A US envoy will visit South Korea on Wednesday as Washington and Pyongyang struggle to find a breakthrough in their stalled talks aimed at ending North Korea’s nuclear program. Stephen Biegun, the US special representative for North Korea, is due to stay four days, Reuters reported, citing a diplomatic source. North Korean leader Kim Jong-un vowed to work toward denuclearization at his summit with US President Donald Trump in Singapore last June. However, the two sides have since made little progress. The stalled negotiations have also had an impact on inter-Korean ties, with the North aloof toward the South’s plan to host Kim in Seoul this month as agreed at his summit with President Moon Jae-in in Pyongyang in September. Kim’s trip is unlikely to take place this year, Moon’s press secretary said last week.