WASHINGTON (AP) — The State Department's top diplomat on Syria is planning to retire by the end of the month, officials said Tuesday, leaving the Obama administration without one of its lead negotiators on one of its biggest security concerns.

State Department officials confirmed that Ambassador Robert Ford has told friends and associates that he plans to leave by the end of February. Ford has been ambassador to Syria since January 2011, but has not lived in Damascus since February 2012, when the State Department suspended embassy operations there.

Since then, he has been a key negotiator in Western efforts to bolster Syrian opposition leaders in their three-year civil war to push Syrian President Bashar Assad from power. Ford also has been instrumental in efforts to unite the fragmented Syrian opposition and get its leaders to negotiations with Assad's regime to broker a peace agreement.

Ford is a longtime Mideast expert who has served in U.S. embassies across the region. Last summer, the White House considered tapping him to become the U.S. ambassador to Egypt. But that never happened amid some objections within the new government in Cairo, which has been irritated over U.S. policy in Egypt.

The State officials who confirmed Ford's departure said there's a slight possibility he might stay for another job, but it was unclear Tuesday what could be offered.

None of the officials were authorized to be identified by name and they spoke on condition of anonymity.