Carter did not personally meet with Kim, but he said that as he and his delegation of former heads of state were on the way to Pyongyang airport to depart for the RoK, they were summoned back to their guesthouse, where a senior official read out a written message from the reclusive leader.

"Chairman Kim sent word that he is willing to negotiate with the RoK or the US ... on any subject at any time and without any preconditions," Carter told a news conference. "He specifically told us he is prepared for a summit directly with President Lee Myung-bak at any time to discuss issues between the two heads of state."

The dramatic declaration puts Lee on the spot: Seoul is currently declining official dialogue with the DPRK until it takes responsibility for two fatal incidents last year.

In 2010, 50 RoKs were killed in the two separate incidents: the RoK accuses the DPRK of torpedoing and sinking one of its warships in March 2010, killing 46 sailors. In November, the DPRK shelled Yeonpyeong Island, killing two RoK marines and two civilians.