The US president has dramatically escalated pressure on the government in Havana and its trade partners

US President Donald Trump has declared a national emergency and threatened to impose steep tariffs on any country supplying oil to Cuba, dramatically escalating pressure on Havana after the US military operation in Venezuela already cut the island nation from its most crucial energy source.

After abducting Venezuelan President Nicolas Maduro earlier this month, the US has set its sights on Cuba, which Trump claims is "ready to fall" next. In an executive order signed on Thursday, Trump branded Cuba "an unusual and extraordinary threat" to US national security.

"The United States has zero tolerance for the depredations of the communist Cuban regime," the order states. "I find that the policies, practices, and actions of the Government of Cuba directly threaten the safety, national security, and foreign policy of the United States."

The order establishes a mechanism to impose potentially severe additional tariffs on imports from any nation caught directly or indirectly selling or providing oil to Havana. It grants broad authority to the Secretaries of State and Commerce to identify violators and recommend tariff levels to the president.

The measure formalizes and intensifies a de facto energy blockade that has been tightening for weeks. The US military operation that captured Venezuelan leader Nicolas Maduro earlier this month cut off Cuba's primary source of crude. Subsequent pressure on Mexico, Havana's last remaining supplier, has left the island facing dire shortages.

Trump predicted on Tuesday that the Cuban government would be "failing pretty soon," boasting that the cutoff of Venezuelan oil and revenue had pushed Havana to the brink. According to data firm Kpler, Cuba has just 15 to 20 days of oil reserves remaining. The country is already enduring daily blackouts, and analysts warn of economic collapse and a humanitarian crisis without rapid resupply.

The White House, in a fact sheet, framed the emergency declaration as a necessary response to malign activity, accusing Cuba of hosting "Russia's largest overseas signals intelligence facility" and providing a "safe environment" for terrorist groups. It also accused Havana of spreading "communist" influence in the Western Hemisphere.

Cuban President Miguel Diaz-Canel has remained defiant, stating earlier this week that "the harshness of these times and the brutality of the threats against Cuba will not hold us back."

Cuba has been under a US trade embargo since the 1960s but has not faced the prospect of an American naval blockade since 1962, when President John F. Kennedy placed it under "quarantine" for 13 days to prevent the transfer of Soviet missiles to the Cuban military.