Pentagon spokesman, Navy Captain Roxie Merritt, on Friday said the US secretary of defence had approved the departure of eligible family members and non-emergency personnel of the Department of Defence from Bahrain.
The move would involve about 650 family members and Defence Department employees from Bahrain, headquarters of the US Fifth Fleet.
It came a day after the State Department issued a travel advisory urging US nationals to defer travel to Bahrain and those in the country to consider leaving because of reports of possible attacks on US and western interests.
Aljazeera's correspondent in Washington quoted a US Defence Department spokesman as saying that Washington was closely monitoring the situation.
"I think that the threat of terrorism is very real, is something that we take very seriously," State Department deputy spokesman Adam Ereli said.
Ereli said: "Clearly there are extremists at large in Bahrain that we are concerned are planning attacks."
It was not immediately clear if the pullout of military dependents was voluntary or compulsory.
The action also halts moves into Bahrain by US military dependents, Merritt said.
US Defence Secretary Donald Rumsfeld ordered the move at the recommendations of the chairman of the Joint Chiefs of Staff, General Richard Myers, chief of naval operations Admiral Vernon Clark, and General John Abizaid, head of US Central Command.