Kim previously called for North Koreans to brace for prolonged COVID-19 restrictions, indicating the nation's borders would stay closed despite worsening economic and food conditions.
US media said Trump scored a diplomatic victory with North Korea releasing the three imprisoned American citizens.
US President Donald Trump confirms Singapore is possible site for summit with North Korean leader Kim Jong Un
Trump confirmed that Singapore was on the list of possible sites, but -- following on from a morning tweet -- he said the Demilitarized Zone should be considered.
US national security adviser John Bolton reacted coolly to word that Kim would abandon his weapons if the United States pledged not to invade.
Trump declared that his nuclear button was "much bigger" and "more powerful" than North Korean leader Kim Jong-un's after the latter threatened the US about Pyongyang's nuclear capabilities.