From the U.S. State Department:
The Department of State continues to warn U.S. citizens against travel to Syria and strongly recommends that U.S. citizens remaining in Syria depart immediately. This Travel Warning supersedes the Travel Warning dated August 28, 2012, to remind U.S. citizens that the security situation remains volatile and unpredictable as an armed conflict between government and anti-government armed groups continues throughout the country, with an increased risk of kidnappings, bombings, murder, and terrorism. ...
For information on "What the Department of State Can and Can't Do in a Crisis," please visit the Bureau of Consular Affairs' Emergencies and Crisis link at www.travel.state.gov. 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 outside the United States and Canada, on a regular toll line at 1-202-501-4444. These numbers are available from 8:00 a.m. to 8:00 p.m. Eastern Daylight Time, Monday through Friday (except U.S. federal holidays).
For further information, U.S. citizens should consult the Department of State's Country Specific Information for Syria. Stay up to date by bookmarking our Bureau of Consular Affairs website, which contains the current Travel Warnings and Travel Alerts as well as the Worldwide Caution.
U.S. State Department Warning