Washington: US President Donald Trump signed an executive order Thursday threatening to impose additional tariffs on countries that sell oil to Cuba, increasing pressure on the communist island nation. The order invokes the International Emergency Economic Powers Act and calls the Cuban government an "extraordinary threat" to US national security. Cuba, which has largely been under a US embargo since 1962, until recently received most of its oil from Venezuela. But since the ouster of Venezuela's autocratic president Nicolas Maduro, Trump has taken the reins of the country's oil sector and has vowed to stop oil shipments to Cuba without an agreement. Another Latin American country, Mexico, continues to provide oil to Cuba, with President Claudia Sheinbaum earlier this week denying reports she had ceased oil shipments to Havana.