In this Feb. 28, 2019, file photo, U.S. President <PERSON>, third from left, speaks with National Security adviser <PERSON>, left, and Secretary of State <PERSON>, second from left, during a meeting with North Korean leader <PERSON>, second from right, in Hanoi, Vietnam. <PERSON> is cautiously turning up the heat after his unsuccessful summit with <PERSON> in Hanoi two months ago.