What issue is North Korea willing to discuss with South Korea according to former U.S. President?

North Korean leader Kim Jong-il is willing to hold a summit with President Lee Myung-bak to discuss denuclearization, former U.S. President Jimmy Carter said Thursday at a press conference after wrapping up a three-day trip to Pyongyang.
    Carter, who visited the North and the South along with three other ex-heads of state, (9) said that Pyongyang was very willing to discuss nuclear issues and any other military issues directly with South Korea including at the highest possible level between Kim Jong-il and the President of South Korea.
    The message came amid a flurry of diplomacy aimed at an eventual resumption of multilateral negotiations on Pyongyang’s denuclearization.
    Seoul, which has indicated it is willing to hold an inter-Korean summit, has yet to respond. The Lee administration had previously attached a summit to apologies for two deadly attacks last year.
    Seoul and Washington want the North to apologize for the sinking of the warship Cheonan in March and the shelling of Yeonpyeong Island before any resumption of the six-party denuclearization talks.
    The six-party talks, which also includes the United States, Japan, Russia and host China, has been on hold since 2009, when Pyongyang walked away in response to international sanctions for its nuclear and missile tests.
                                                                    USA Today