North Korea is testing an engine that would be used on their long range missiles which could concievably hit cities on the US west coast:

A previously unknown missile launch site on the west coast of North Korea was identified last week by Jane's Defense Weekly, which cited commercial satellite images. The facility has a mobile launch pad and a 10-story tower that would support the North's largest ballistic missiles, Jane's reported.

Appearing before a parliamentary committee in Seoul on Thursday, South Korean Defense Minister Lee Sang-hee said the launch site is about 80 percent complete. His remarks added to the growing body of information about the site in recent media reports.

If accurate, the reports indicate that while North Korea has pursued on-again, off-again negotiations with the United States and four other countries on abandoning its nuclear weapons program, it has continued to work on developing a long-range ballistic missile and is diverting scarce resources from a collapsing economy that has brought about chronic food shortages.

A 2006 U.N. Security Council resolution demands that North Korea "suspend all activities related to its ballistic missile program." The North must abandon its program in a "complete, verifiable and irreversible manner," the resolution says.