WASHINGTON — Senior U.S. officials say the United States is pulling roughly 60 percent of its staff out of Cuba and warning American travelers not to visit due to "specific attacks" that have harmed U.S. diplomats.

The officials say the U.S. is ordering all nonessential staff in the embassy in Havana to leave, along with all family members. Only "emergency personnel" will remain.

The U.S. is also warning American citizens they could be harmed if they travel to Cuba. A State Department travel warning will note that attacks on diplomats have occurred in hotels.

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The officials say the U.S. is halting visa processing in Cuba indefinitely. They say the steps will remain until Cuba can assure the U.S. its diplomats are safe.

The officials weren't authorized to comment publicly and demanded anonymity.

CBS News reported Thursday that the U.S. had been preparing a major withdrawal of staff and family from the U.S. embassy in Cuba in response to attacks targeting diplomats.

An internal memo was sent to Secretary of State Rex Tillerson suggesting a drawing down of personnel in Havana. The meeting this week between Tillerson and Cuban Foreign Minister Bruno Eduardo Rodriguez Parrilla did nothing to help assure the U.S. that Cuban officials are doing enough to protect the safety and welfare of U.S. diplomats in their country. Though Cuba is allowing U.S. investigators into the country, it has not convinced the U.S. that it's taken any real action to prevent the health attacks.

Diplomats have complained about symptoms ranging from hearing loss and nausea to headaches and balance issues after the State Department said "incidents" began affecting them in late 2016. In total, the State Department says there are 21 medically confirmed cases. The attacks were directed at their homes, which the Cuban government provides. The last reported incident was in August.