September 2014, President Obama:

… “This counter-terrorism campaign will be waged through a steady, relentless effort to take out ISIL wherever they exist using our air power and our support for partner forces on the ground. This strategy of taking out terrorists who threaten us, while supporting partners on the front lines, is one that we have successfully pursued in Yemen and Somalia for years.”

Today, Via U.S. State Department – Due to the recent resignation of the Yemeni president, prime minister, and cabinet, and the ongoing security concerns, the U.S. Embassy in Sanaa is unable to provide routine consular services and will have very limited ability to assist with emergency cases involving U.S. citizens.
The U.S. Embassy will be closed to the public until further notice out of an abundance of caution and care for our employees and others who may be visiting the Embassy. We are continuously analyzing the security conditions and will resume consular operations as soon as our analysis indicates we are able to do so safely.
The U.S. Department of State warns U.S. citizens of the high security threat level in Yemen due to terrorist activities and civil unrest. The Department urges U.S. citizens not to travel to Yemen. U.S. citizens still in Yemen should make plans to depart immediately. U.S. citizens seeking to depart Yemen are responsible for making their own travel arrangements. Travelers should reconfirm flight schedules with their airline prior to going to the airport. Flight cancellations occur frequently. There are no plans for charter flights or other U.S. government-coordinated evacuations.
U.S. citizens in Yemen remain vulnerable to kidnappings and terrorist attacks, especially when in transit to and from residences or workplaces. U.S. citizens should exercise caution and take prudent security measures in all areas, especially those areas frequented by Westerners. All U.S. citizens are reminded to vary their routes and times for all travel, maintain a high level of vigilance, keep a low profile, lock car windows and doors, carry a cell phone at all times, and report suspicious incidents to the Embassy. (more)