According to the Drudge Report, describing an article by Bill Gertz:
The Pentagon activated its new U.S. ground-based interceptor missile defense system, Bill Gertz reports in Tuesday's WASHINGTON TIMES, just as officials announced that any long-range missile launch by North Korea would be considered a "provocative act."
Two Navy Aegis warships are patrolling near North Korea as part of the global missile defense and would be among the first sensors that would trigger the use of interceptors, the officials said yesterday.
Full article: http://www.washtimes.com/national/20060620-123010-4554r.htm
U.S. Northern Command - http://www.northcom.mil/about_us/about_us.htm
U.S. Strategic Command - http://www.stratcom.mil/
U.S. Air Force Space Command - http://www.afspc.af.mil/
[Edited 2006-06-20 09:40:04]