From the U. S. State Department:
The Department of State warns U.S. citizens against travel to Afghanistan. The security threat to all U.S. citizens in Afghanistan remains critical. This Travel Warning supersedes the Travel Warning for Afghanistan issued on August 23, 2013.
No province in Afghanistan should be considered immune from violence and banditry, and the strong possibility exists throughout the country for hostile acts, either targeted or random, against U.S. and other foreign nationals at any time. Remnants of the former Taliban regime and members of other terrorist organizations hostile to the Government of the Islamic Republic of Afghanistan and foreign nationals remain active in every province of the country. Furthermore, travel to all areas of Afghanistan remains unsafe due to ongoing military combat operations, landmines, banditry, armed rivalry between political and tribal groups, and the possibility of insurgent attacks, including attacks using vehicle-borne or other improvised explosive devices. The threat situation in Afghanistan is still considered critical and is expected to remain so through the presidential and provincial elections and the political and military transition in 2014. …
For the latest security information, U.S. citizens living or traveling abroad should regularly monitor the Department of State’s Consular Affairs’ website where the current Worldwide Caution, Travel Alerts and Travel Warnings, and Country Specific Information for Afghanistan can be found. Up-to-date information on security can also be obtained by calling 1-888-407-4747 toll free in the United States and Canada or, for callers in other countries, by calling a regular toll line at 1-202-501-4444. These numbers are available 8:00 a.m. to 8:00 p.m. Eastern time, Monday through Friday (except U.S. federal holidays).Caution, which are available on the Bureau of Consular Affairs Internet website. You can also stay up to date by bookmarking our Bureau of Consular Affairs website, which also contains current Travel Warnings and Travel Alerts.
U.S. State Department Warning