The Havana government on Thursday denied US news reports that it has reached a deal for China to set up a spying base in Cuba, just off American shores.
Cuba's deputy foreign minister said the reports by The Wall Street Journal and CNN were "mendacious and unfounded." The White House called them inaccurate.
The reports said Beijing and Havana have entered into a secret agreement for a Chinese electronic eavesdropping facility to be set up on the Caribbean island that could monitor communications across the southeastern US.
The region includes the US Southern and Central Command headquarters, both in Florida.
China will pay Cuba "several billion dollars" to be able to construct the facility, WSJ said, citing unnamed US officials.
But Cuban Deputy Foreign Minister Carlos Fernandez de Cossio, reading a statement to journalists, called the reports "totally mendacious and unfounded."
He said Cuba rejects all foreign military presence in Latin America, "including the many US bases and troops."
"Slander of this kind is often fabricated by US officials," the official said.
White House national security spokesman John Kirby characterised the WSJ story as inaccurate.
"I've seen that press report. It's not accurate," Kirby told MSNBC.
"What I can tell you is that we have been concerned since day one of this administration about China's influence activities around the world, certainly in this hemisphere and in this region," Kirby said.
"We are watching this very closely," he added.
Pentagon spokesman Pat Ryder also called the WSJ report inaccurate.
"We are not aware of China and Cuba developing any type of spy station," Ryder said, adding: "The relationship that those two countries share is something that we continuously monitor."
But Democratic senator Mark Warner and Republican Marco Rubio, who head the Senate Intelligence Committee and are usually briefed on important security matters, said in a statement that they were "deeply disturbed" by the WSJ report.
"The US must respond to China's ongoing and brazen attacks on our nation's security," they said.
"We must be clear that it would be unacceptable for China to establish an intelligence facility within 160km of Florida and the US."
The WSJ story came amid strained relations between Washington and Beijing over a range of issues that include US support for self-ruled Taiwan, which China says it is determined to reunite with the mainland.
Chinese leader Xi Jinping has pushed a rapid expansion of the country's security presence around the world, aiming to match the broad footprint of the US military on all the continents.
A base in Cuba, which lies 90 miles off Florida's southern tip, would present the most direct challenge yet to the continental US.
The Soviet Union had electronic spying facilities in communist Cuba to monitor the US.
But in 1962 when Moscow moved to base nuclear missiles on Cuba, the US 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 US. It floated from west to east above sensitive military installations before it was shot down by a US fighter jet.