U.S. officials Tuesday condemned North Korea's deadly attack on South Korea, pledged to protect an ally and urged China to take a more punitive stance toward Kim Jong Il's regime than it has in the past.http://www.miamiherald.com/2010/11/23/1940773/korean-showdown-puts-unity-to.html
Still, they also said it's "too soon" to know how to formally respond.
North Korea has the nuclear material, the missiles, and the technology. Soon, they'll have nuclear armed intercontinental missiles. At that point, sternly worded protests will be ineffective.