The State Department, apparently concerned about possible strikes on American targets by Syrian government allies, on Friday ordered nonessential diplomats at the United States Embassy in Beirut and their families to leave Lebanon.

The department also said nonessential diplomats and their families could leave the American Consulate in Adana, in southern Turkey near the Syrian border, but did not issue an order.

Both diplomatic posts remain open, though with fewer staff members and more limited operations. On Friday, the department also issued travel warnings urging Americans to avoid southeastern Turkey and Lebanon.

The moves appear to reflect concern that supporters of the Syrian government, like Hezbollah or Iran, might carry out or encourage terrorist attacks on United States diplomats in retaliation for an American-led military strike to punish the government of President Bashar al-Assad of Syria for a chemical weapons attack last month.