The United States offered talks with North Korea to formalize a peace treaty with the South just before Pyongyang conducted a nuclear test explosion last month, a news report said.
Washington dropped a long-standing provision that North Korea start to rein in its nuclear arms programme before any such talks, saying instead that the question of the nuclear weapons should be included in the agenda for the talks themselves.
Pyongyang declined and held its fourth nuclear test on January 6 in apparent response, the Wall Street Journal reported late Sunday, citing unnamed government officials.
The two Koreas remain technically at war since the 1950 to 1953 conflict, in which the US fought alongside the South, ended in a ceasefire rather than a peace treaty. The proposed talks would aim to draw up a formal treaty.
North Korea followed the January 6 explosion with a rocket launch the next day, which Pyongyang said was to put a satellite in space, but which the international community condemned as a test of nuclear-capable technology, prompting several fresh sanctions.