The United States is closing its embassy in Yemen, the Arabian peninsula state that is a front line in Washington's war against al Qaeda, embassy employees and U.S. officials said on Tuesday.

U.S. officials in Washington confirmed the embassy would close because of the unpredictable security situation in a country where a rebel group has seized control of the capital, Sanaa.

State Department spokeswoman Jen Psaki declined comment. But she noted that the embassy staff had been gradually reduced and said the safety of the personnel was a top priority. "We take steps in order to make sure we do everything we can to protect that," she told a regular briefing.

One U.S. official said a contingent of around 100 Marines was helping protect the U.S. embassy in Yemen. Another official said a Navy amphibious assault ship, the USS Iwo Jima, was in the Red Sea off Yemens coast and would be available to help with the evacuation of embassy staff, if requested by the State Department.