A senior South Korean official has urged China to serve as a 'catalyst' for the peaceful reunification of the two Koreas. But the same official could not rule out US troops retaining a presence in a future combined state. Kim Chun-sig, South Korea's deputy unification minister, said Seoul was sticking to its long-term goal of peaceful and gradual integration with the North following the rise of Kim Jong-un after the death of his father, Kim Jong-il, in December. 'As to China's role in Korean unification ... first of all peace must be maintained on the Korean Peninsula, and the homogeneity of the Koreas must be promoted through exchanges and co-operation. I hope China can serve as a catalyst to this process,' he said. 'And a unified Korean Peninsula will be better able to maintain peace and stability in the East and Northeast Asian region, which is conducive and serves the interests, I believe, of China.' Kim Chun-sig's remarks, in a recent, wide-ranging interview, underscore Seoul's enduring dilemma. On the one hand, it must prepare to absorb the world's most isolated - and now one of its poorest - states, while on the other, the North remains hostile to its old enemy, with tensions rising in recent years. Seoul is eagerly watching Pyongyang-Washington talks this week following last week's deal for the US to provide food aid while North Korea halts nuclear work and military provocations - the most significant move in three years. While Kim Chun-sig said that, realistically, war was unlikely on the Korean Peninsula, North Korea had never ruled out the use of force to unite the two Koreas and 'there was always a possibility of war'. Then there is the role of China, Pyongyang's lifeline and long-standing fraternal ally. While Seoul officially welcomes and encourages Beijing's work to stabilise the Korean Peninsula and push Pyongyang to denuclearisation talks, South Korean officials privately fear that Beijing remains leery of any unification outcome that would put a Western-aligned nation on its borders. Asked whether Seoul's vision of a unified Korea still had a place for US troops, Kim Chun-sig said it was inappropriate to discuss such a matter. But he quoted former president Kim Dae-jung's remarks that the ongoing presence of US troops in a unified Korea would be 'conducive to the stability and peace on the Korean Peninsula and Northeast Asia'. His comments come amid a testing time for Sino-South Korean relations. Seoul is attempting to raise international concern over Beijing's ongoing repatriation of North Korean defectors - while Seoul insists they are refugees at risk of punishment who should be resettled in South Korea, China insists they are economic migrants who should be sent home. The issue dominated talks in Seoul last Friday between Foreign Minister Yang Jiechi and South Korean leaders including President Lee Myung-bak, with Yang warning against further efforts to internationalise the issue. Overall, Kim Chun-sig said Seoul was still sticking to its goal of gradual institutional unification engineered through dialogue and co-operation - and backed by massive infrastructure spending from the South. Privately, however, some South Korean officials acknowledge that such hopes may be in vain should the Kim dynasty's grip on Pyongyang's elite collapse - forcing a swifter and potentially dangerous merger. The regime of Kim Jong-un had so far offered no signals about talks, either about unification or otherwise, officials said. 'The South Korean government does not pursue the collapse of North Korea nor do we want North Korea to collapse and we refrain from discussing things on the assumption that North Korea will collapse,' Kim Chun-sig said. 'In any case, it will be the North Korean people who will decide ... on their own fate.'