Here's the State Department Travel Warning, first paragraph.
This supersedes the Worldwide Caution dated November 21, 2003. The text of that Caution is being reiterated below to remind U.S. citizens of the continuing threat that they may be targets of terrorist actions and to alert them to the raising of the Homeland Security threat level from Yellow (Elevated) to Orange (High). This Worldwide Caution expires on June 21, 2004.