WASHINGTON - In a move that casts doubt on the state of a historic detente between two longtime rivals, the United States has ordered a sudden reduction in its diplomatic staff in Cuba, cutting the majority of its presence at the Havana embassy in the wake of bizarre injuries to employees.

Announcing the move Friday, American officials linked it to 21 injuries from what they have begun describing as sonic ''attacks,'' with symptoms including ear complaints, hearing loss, dizziness, headache, fatigue, cognitive problems and difficulty sleeping.

It's unclear what caused the problems and the FBI has been working with the Cuban government to determine who or what is responsible and whether the harm was intentional or the result of defective spying equipment.

The U.S. is maintaining diplomatic ties with Cuba, re-established under former president Barack Obama. But in addition to withdrawing about 60 per cent of its diplomatic staff, it is also limiting visas for Cuban visitors. Remaining in the embassy will be the core staff necessary to handle emergencies.

''The health, safety, and well-being of our embassy community is our greatest concern. We will continue to aggressively investigate these attacks until the matter is resolved,'' Secretary of State Rex Tillerson said.

''The decision to reduce our diplomatic presence in Havana was made to ensure the safety of our personnel. We maintain diplomatic relations with Cuba, and our work in Cuba continues to be guided by the national security and foreign policy interests of the United States.

''Cuba has told us it will continue to investigate these attacks and we will continue to co-operate with them in this effort.''

Canada is not following the Trump administration's move.

''We do not have any reason to believe Canadian tourists and other visitors could be affected,'' said a statement from the Canadian government.

''Canada currently has no plans to change its travel advice and advisory for Cuba or remove its staff from Cuba.''

While several Canadian diplomats and their families also suffered injuries earlier this year, there have been no repeat incidents since the spring. The northern neighbour has long had normal diplomatic relations with Cuba, unlike the U.S. whose relationship was marked by decades of political estrangement, mass migration and ongoing economic sanctions that have opened a sliver in recent years.

The historic move to reopen embassies in Havana and Washington came after lengthy, secret negotiations facilitated by the Vatican and the Canadian government. But the biggest U.S. critics of the Castro regime opposed the reopening.

And some of them challenged Friday's move as not severe enough.

''Shameful,'' tweeted Sen. Marco Rubio, the son of Cuban immigrants. ''(The State Department) withdraws most staff from (the U.S. embassy) but Castro can keep as many as he wants in U.S.''

News from © The Canadian Press, 2017