More Cheonan...

The United States is pledging its support for Seoul:

U.S. President Barack Obama expressed his full backing for South Korea and its investigation into the sinking of the Navy vessel Cheonan near the inter-Korean West Sea border, Cheong Wa Dae said Tuesday.

President Lee Myung-bak and Obama spoke over the phone for about 25 minutes earlier to discuss a joint response to the naval tragedy.

"Obama told Lee that he fully trusts Seoul and backs its handling of the incident," the presidential office said in a press release.

Obama said Secretary of State Hillary Clinton will fly to Seoul next week to discuss the case, adding the U.S. will closely cooperate with South Korea to deal with the aftermath. Clinton is scheduled to hold high-level meetings in Beijing from May 24 to 25.

And South Korea is preparing to formally blame Pyongyang for the attack:

South Korea will formally blame North Korea on Thursday for launching a torpedo at one of its warships in March, causing an explosion that killed 46 sailors and heightened tensions in one of the world's most perilous regions, U.S. and East Asian officials said.

South Korea concluded that North Korea was responsible for the attack after investigators from Australia, Britain, Sweden and the United States pieced together portions of the ship at the port of Pyeongtaek, 40 miles southwest of Seoul. The Cheonan sank on March 26 after an explosion rocked the 1,200-ton vessel as it sailed on the Yellow Sea off South Korea's west coast.

The officials, who spoke on the condition of anonymity because South Korea has yet to disclose the findings of the investigation, said subsequent analysis determined that the torpedo was identical to a North Korean torpedo that South Korea had obtained.

Of the countries aiding South Korea in its inquiry, officials said that Sweden had been the most reluctant to go along with the findings but that when the evidence was amassed, it too agreed that North Korea was to blame. A spokesman for the Swedish Embassy declined to comment.

Will Ruger and I have an op-ed in the Korea Times:

President Lee needs to find a Goldilocks solution to the crisis.

He must craft a policy that is neither so aggressive as to provoke a spiral into general war with all of its associated human and economic costs, nor so meek that North Korea is emboldened, the demands of justice for the dead and wounded sailors unmet, and the public's security concerns undiminished.

Lee needs to send an appropriate message that answers the North Korean challenge. However, this is not merely a two party conversation. The situation is complicated by the fact that South Korea must send messages to at least three different audiences ― and they must be clear enough to be properly understood.

To the people of South Korea, the government must show that the armed forces are capable of responding to North Korean aggression.

It must tell them it will not allow their sons to be killed with impunity even if that comes at a cost in blood and treasure. To the international community, Seoul must craft a careful, measured response indicating its understanding of the delicacy of the regional situation and portraying itself as the responsible party.

The message sent to the North Korean government must be that aggression will result in painful consequences so that in the future Pyongyang will not believe that it can act with impunity.