Diplomats have 7 days to leave.
The State Department said Tuesday it is expelling 15 officials from Cuba's embassy in Washington in response to a series of mysterious "attacks" medically affecting almost two dozen American diplomats.
The move does not a signal a change in policy or determination of responsibility for the attacks, a State Department official who asked not to be named, told reporters..
"We are not assigning culpability. This is to ensure that there is an equitable impact to our embassies’ ability to operate, and to underscore to the Cubans that they must take more action to protect our people on the ground," the official said.
The official would not get into what action Washington expected Havana to take, given the inscrutable nature of the attacks.
The Cuban officials, who the State Department identified on a list sent to the embassy, have been given seven days to leave, the official said.
The U.S. on Friday made dramatic cuts to its diplomatic presence in Cuba and warned Americans to avoid travelling to the island after the attacks, the latest of which happened in August.
The recently re-opened U.S. embassy in Cuba will have its staffing reduced to emergency personnel only, and visa operations have been suspended indefinitely as a result of the action.
"The decision to reduce our diplomatic presence in Havana was made to ensure the safety of our personnel," Secretary of State Rex Tillerson said in a statement.
Twenty-one U.S. diplomats have suffered various physical ailments from the attacks, acknowledging the nature remains unknown as well as the perpetrators.
U.S. officials had previously refrained from calling it "attacks", instead using the vague language of "incidents".
Victims have suffered a range of symptoms including hearing loss, ear problems, dizziness, headache, cognitive issues and fatigue.
Havana has pledged to continue to investigate and the U.S. will assist in the effort, Tillerson said.