US President Donald Trump signed an executive order Thursday threatening to impose additional tariffs on countries that sell oil to Cuba, further increasing pressure on the communist-led island.

The order did not specify the value of the tariffs or which countries would be targeted, leaving those determinations up to his secretary of commerce.

Cuba, which has largely been under a US embargo since 1962, until recently received most of its oil from Venezuela.

But the United States has moved to block the flow after removing Havana’s key ally Nicolas Maduro from power and effectively seizing control of Venezuelan oil exports.

Following the Venezuela operation, Trump vowed to completely cut off oil and money going to Cuba.

“I strongly suggest they make a deal, BEFORE IT IS TOO LATE,” he threatened in a social media post.