North Korean leader Kim Jong Un said a U.S.-South Korea joint military exercise could "ignite a war" and called for the rapid expansion of Pyongyang's nuclear capabilities.

FILE – Kim Yo Jong, the powerful sister of North Korean leader Kim Jong Un, attends a wreath-laying ceremony at Ho Chi Minh Mausoleum in Hanoi, Vietnam, March 2, 2019. (Jorge Silva/Pool Photo via AP, File)

Kim Yo Jong, a senior official on the State Affairs Commission, called South Korean President Lee Jae-myung’s push for improved ties a “pipe dream,” according to a statement published by the Korean Central News Agency. She accused Lee or trying to create an “amicable image” while hosting a large-scale military exercise with the United States.