South Korean President Lee Jae Myung said North Korea continues to produce nuclear material at a pace that could allow it to add up to 20 nuclear weapons a year, underscoring concerns that Pyongyang has no intention of slowing its nuclear program.

South Korea said Friday it believes North Korea remains committed to improving relations despite strongly criticizing Seoul over ongoing U.S.-South Korean military drills and insisting it will not return to inter-Korean talks unless its grievances are ...