It follows a series of unexplained incidents on diplomats
The United States is pulling 60% of its staff out of Cuba and urging Americans not to visit the country after a series of targeted attacks injured its diplomats.
According to the State Department, the symptoms of the 21 harmed embassy workers included "hearing loss, dizziness, tinnitus, balance problems, visual complaints, headache, fatigue, cognitive issues and difficulty sleeping".
Some were left with serious conditions such as permanent hearing loss and traumatic brain injury.
All non-essential staff and their families at the embassy in Havana have been ordered to leave, with only "emergency personnel" allowed to remain.
Some of the attacks on diplomats have occurred in hotels - and while the US does not believe Cuba is behind the attacks, it has yet to establish the source.
In response, Cuba has said the US decision to reduce staffing at the embassy in Havana is hasty and likely to affect relations between the two.
The US is halting visa processing in Cuba indefinitely, and officials say the steps will remain until Cuba can offer assurance that American diplomats will be safe.
But last week, Cuban Foreign Minister Bruno Rodriguez Parrilla said Havana has found no evidence to support Washington's claims that US diplomats were harmed due to the attacks.
US Secretary of State Rex Tillerson has said America will maintain diplomatic ties with Cuba despite the attacks, adding: "Our work in Cuba continues to be guided by the national security and foreign policy interests of the United States."
US officials have said the Trump administration had considered ordering Cuban diplomats to leave Washington - but for now, such a move will not take place.
No American tourists have been harmed in the attacks, but there are concerns they could be exposed to danger if they travel to Cuba.
Tourism is a critical component of the Caribbean island nation's economy, and the industry has grown in recent years after the US relaxed restrictions.