The Wall Street Journal reported that Beijing and Havana have entered into a secret agreement for a Chinese electronic eavesdropping facility on the Caribbean island that could monitor communications across the southeastern United States.

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, the Wall Street Journal said, citing unnamed US officials.

The Pentagon would not confirm or deny the report, which comes amid strained tensions between Washington and Beijing over US support for self-ruled Taiwan, which China says it is determined to reunite with the mainland.

"We are not going to comment on those specific reports," said a US Defense Department official on grounds of anonymity.

"On a broader level, we are very aware of the PRC's attempts to invest in infrastructure around the world that may have military purposes, including in the western hemisphere," the official said, using an acronym for the People's Republic of China.

"We will continue to monitor it closely, and remain confident that we are able to meet all our security commitments at home and across the region."

Chinese leader Xi Jinping has pushed a rapid expansion of the country's security presence around the world, aiming to match the broad presence of the US military on all the continents.

A base in Cuba, which lies just 90 miles (150 kilometers) off the south coast of Florida 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 US declared a quarantine of the island that threatened to bring the two superpowers to war, until Moscow backed down on its plans.

Washington then removed its nuclear-capable missiles from Turkey, which the Soviets viewed as a threat to them.

The Chinese move with Cuba comes after China sent a high-altitude surveillance balloon across the United States earlier this year, floating from west to east above sensitive military installations before it was shot down just off the east coast by a US fighter jet.