The denuclearization of North Korea remains an unexpendable issue for South Korea even as Seoul prepares for talks with Pyongyang over a pair of other security issues, an official said Friday.

   The comments by Unification Ministry spokesman Chun Hae-sung mean that South Korea will continue to press North Korea to agree to separate talks on the nuclear programs the communist state operates.

   On Thursday, North Korea proposed holding "high-level" military talks with South Korea on the Nov. 23 artillery exchange between the sides and the sinking of a South Korean warship in March last year.

   South Korea accepted the proposal within hours, after having refused for weeks to hold talks with the North until Pyongyang was ready to discuss the sinking of the Cheonan, its artillery attack on Yeonpyeong Island and its nuclear arms ambitions.

   "High-level governmental talks are also needed to confirm (North Korea's) commitment to denuclearization, which is the most important pending security issue," Chun said in a briefing.

   North Korea argues its nuclear programs must be negotiated mainly with the United States because its atomic weapons are aimed at deterring an American invasion. Since a conservative government took power in 2008, South Korea, however, has demanded the issue be discussed also with Seoul in bilateral dialogue because atomic bombs pose the greatest threat to its national security.

   The proposal on Thursday, signed by North Korea's defense minister and addressed to his South Korean counterpart, came on the heels of a joint statement by U.S. President Barack Obama and Chinese President Hu Jintao in Washington, which called for sincere and constructive dialogue between the Koreas as an "essential step."

   In a related development, South Korea's defense ministry said Friday that it plans to propose holding a preparatory meeting with North Korea next week ahead of the high-level inter-Korean talks.

   The defense talks, if held, will be the first between the divided Koreas since North Korea's artillery attack on the western South Korean island killed two marines and two civilians and raised regional tensions to the highest level in years, if not decades.

   North Korea argues it attacked because the South first fired at its side. Concerning the March sinking of the Cheonan warship, North Korea denies any role, demanding that Seoul accept an inspection team from Pyongyang to jointly verify its cause.

   In May, a multinational investigation team led by Seoul concluded that a North Korean torpedo sank the ship, killing 46 sailors in the Yellow Sea.

   Unveiling its proposal through the official Korean Central News Agency, North Korea said Friday it is "firmly willing to resolve all pending military issues" during its high-level talks with the South.

   The proposal went on to say that the agenda would be "about defusing the state of military tension on the Korean Peninsula and the expression of opinions on the Cheonan incident and the Yeonpyeong artillery exchange," the KCNA said.

   South and North Korea remain technically at war after the

1950-53 Korean War ended in a truce rather than a peace treaty.