China warned the United States Friday against "interfering in Cuba's internal affairs", in response to reports that Beijing was planning to set up a spy base on the island just off American shores.
The media reports, based on comments by anonymous US officials to The Wall Street Journal and CNN, were dismissed by Cuba's deputy foreign minister as "mendacious and unfounded", while the White House called them inaccurate.
When asked about the alleged spying base at a regular press briefing, Chinese foreign ministry spokesperson Wang Wenbin said he was "unaware of the situation" before criticising US policy on Cuba.
"As we all know, spreading rumours and slander is a common tactic of the United States, and wantonly interfering in the internal affairs of other countries is its patent," said Wang.
"The United States should reflect on itself and stop interfering in Cuba's internal affairs under the banner of freedom and democracy, and immediately cancel the economic, commercial and financial embargo against Cuba."
The reports suggested that the Chinese spying base would be capable of eavesdropping on communications across broad swathes of the southeastern United States.
The developments come as Chinese leader Xi Jinping has pushed a rapid expansion of the country's security presence around the world.
A base in Cuba, which lies 90 miles (150 kilometres) off Florida's southern tip, would present the most direct challenge yet to the continental United States.
The Soviet Union had electronic spying facilities in communist Cuba to monitor the United States.
But in 1962 when Moscow moved to base nuclear missiles on Cuba, the United States declared a quarantine of the island in a crisis that threatened to bring the two superpowers to war, until Moscow backed down.
Washington then removed its nuclear-capable missiles from Turkey, which the Soviets viewed as a threat to them.
Earlier this year, China sent what the US called a high-altitude surveillance balloon across the United States. It floated from west to east above sensitive military installations before it was shot down by a US fighter jet.