US Hellfire missile wrongly shipped to Cuba
An inert US Hellfire missile sent to Europe for a training exercise was wrongly shipped on to Cuba, the Wall Street Journal reports.
The incident in 2014 could have led to a serious loss of military technology, officials told the paper.
US officials have since been trying to get Cuba to return the missile, which did not contain explosives.
Investigators are unclear if the incident was an error or the result of espionage, the paper says.
A US official "with knowledge of the situation", who was not authorised to speak publicly on the matter and demanded anonymity, confirmed the report's veracity to The Associated Press.
The Hellfire is a laser-guided missile that can be deployed from an attack helicopter or an unmanned drone.
Quoting sources close to the investigation, the Wall Street Journal said that the missile had been shipped to Spain in early 2014 to be used in a Nato training exercise.
It was then taken through Spain and Germany and eventually to Charles de Gaulle Airport in Paris where it was to be shipped back to Florida.
However, it was instead loaded on to an Air France flight to the Cuban capital, Havana.
US officials are worried that Cuba could share the advanced technology inside the missile with countries such as North Korea, China or Russia, the paper adds.
The US and Cuba, once Cold War foes, restored diplomatic relations in July last year.