Secretary of State Hillary Clinton warned North Korea today that it must "halt its provocations" as she reaffirmed the United States' strong support of South Korea.
Speaking in Seoul at the end of her trip across Asia, she called on the international community to make a "strong but measured response" to the sinking of a South Korean warship that has been blamed on North Korea.
Clinton refused to be drawn out on the timing of a response or what it might entail. But she was emphatic that the international investigation which found North Korea responsible for the sinking was "very thorough, highly professional" and "the evidence overwhelming."
Clinton flew in from Beijing where she has been trying to persuade Chinese leaders to support U.N. Security Council action against North Korea.
"I believe that the Chinese understand the seriousness of this issue and are willing to listen to the concerns expressed by both South Korea and the United States," she said. "We expect to be working with China as we move forward in fashioning a response."
South Korea has already announced a package of reprisals, including an end to nearly all trade with the North. And they are pushing for more sanctions at the UN Security Council, but need China's support.
Thursday, South Korea will go ahead with military exercises in the waters off its coast. Joint exercises with the United States are in the planning stages, an action designed to remind the North what it is up against and one that is likely to anger North Korean leader Kim Jong-Il.
The United States has 28,500 troops stationed in South Korea and Secretary Clinton said today it is "reviewing additional options…to hold North Korea and its leaders accountable."
The North, which continues to deny involvement in the naval attack, has said it is cutting all ties with the South. Today it severed two lines of communication, a hotline and maritime communications system.
It warned it would close the last land link across the border if South Korea goes ahead with its plans to use speakers to broadcast propaganda into the North. It also said it would blow up the speakers. South Korean ships and planes are now banned from using the North's waters and airspace.
Experts say it is highly unlikely that North Korea will admit guilt in the attack for a number of reasons.
First, there is the ongoing sea battle between the two Koreas at the disputed maritime border in the Yellow Sea. Last November, North Korea crossed the maritime border, South Korea fired warning shots which the North did not heed and a firefight ensued.
The North Korean ship was believed to have been hit, but they did not confirm what would have been an embarrassment for a regime which constantly flouts its "military might."
The other is the issue of succession in North Korea, as rumors continue to circulate about Kim Jong Il's health.
"My gut feeling is that we could be entering the dynamics of that transition process," Daniel Pinkston, deputy director of Northeast Asia project for the International Crisis Group in Seoul, told ABC News.