The fallout from the sinking of the Cheonan is causing a diplomatic dilemma for China, which has important strategic links with both countries on the Korean Peninsula.

In recent years China has carefully cultivated relationships with both North and South Korea, glossing over the apparent contradiction in maintaining close ties with two sworn enemies.

In doing so, China has become one of South Korea's biggest trade partners, while continuing to support Seoul's authoritarian neighbour.

But with the South demanding action against North Korea for its apparent role in sinking the Cheonan, those relationships, painstakingly built through years of regional summits and bilateral diplomacy, have taken a blow.