Days before North Korea’s latest nuclear-bomb test, the Obama administration secretly agreed to talks to try to formally end the Korean War, dropping a longstanding condition that Pyongyang first take steps to curtail its nuclear arsenal.

Instead the U.S. called for North Korea’s atomic-weapons program to be simply part of the talks. Pyongyang declined the counter-proposal, according to U.S. officials familiar with the events. Its nuclear test on Jan. 6 ended the diplomatic gambit.