The South Koreans will formally announce that North Korea was behind the sinking of the Cheonan.
The Washington Post reports:
South Korea will request that the U.N. Security Council take up the issue and is looking to tighten sanctions on North Korea, the officials said. The United States has indicated it would support such an action, U.S. officials said. Japanese Foreign Minister Katsuya Okada told his South Korean counterpart on Monday that Japan would do the same, the Japanese press reported Tuesday.
Another consequence of the report, experts predicted, is that Lee will request that the United States delay for several years a plan to pass operational control of all forces in South Korea from the United States to the South Korean military. Approximately 28,500 U.S. forces are stationed in South Korea.
South Korea's conclusion that North Korea was responsible for the sinking of the Cheonan also means it is unlikely that talks will resume anytime soon over North Korea's nuclear weapons program. North Korea has twice tested what is believed to be a nuclear weapon. China has pushed for an early resumption of those talks, but South Korean officials said they will return to the table only after there is a full accounting for the attack against the Cheonan and a policy response.
Scott Snyder analyzes South Korea's response:
Finally, the Lee administration made an early bet that internationalizing the Cheonan response would be the most effective South Korean course of action. Involving international investigators shields the South from accusations that the investigation is biased, but thus far it appears to have yielded little political influence with China, who has applauded South Korea’s decision to undertake a “scientific and objective investigation.” Furthermore, China’s decision to host Kim Jong Il less than a week following Lee Myung-bak’s visit was taken very poorly in Seoul, potentially revealing the limits of South Korea’s internationalization strategy. China is unlikely to accept condemnation of North Korea at the UN Security Council without a “smoking gun” that directly links North Korea to the Cheonan incident.
South Korea’s international approach casts China as the enabler of North Korean provocations. South Korea’s approach attempts to impose potential costs on China as a proxy for South Korean inability to impose costs directly on North Korea. In this approach, China’s failure to rein in North Korea will have costs to China’s interests on the Korean peninsula (as enumerated in my recent CSIS report with Bonnie Glaser on the need for Sino-U.S.-ROK dialogue to plan for instability in North Korea) in the form of increased South Korean public hostility toward China, increased regional tensions on China’s periphery, and by making China North Korea’s guardian at the UN. It remains to be seen whether South Korea’s post-Cheonan diplomacy will influence China’s approach to the peninsula.
Much has been made of China's "soft power" push in Asia, but alienating Japan and South Korea to curry favor with North Korea doesn't seem like a sustainable strategy to me.