United States President Donald Trump on Tuesday ordered a blockade of sanctioned oil vessels heading to and leaving Venezuela.

The decision escalates Washington’s military and economic pressure campaign on the Nicolás Maduro government in Venezuela. The South American country’s economy is heavily dependent on oil export.

Trump said that Venezuela had been “completely surrounded by the largest armada ever assembled in the history of South America”, adding that “it will only get bigger”.

Since late August, the US has put together a major military deployment off the Venezuelan coast with the stated goal of combatting drug trafficking in Latin America, but has focused on Venezuela.

On Tuesday, the US president said that his country wanted to regain oil that he claimed had been stolen by Venezuela.

“…the shock to them [Maduro government] will be like nothing they have ever seen before – until such time as they return” to the US “all of the oil, land and other assets that they previously stole from us”, Trump said on social media.

It was unclear what oil or land Trump was referring to. Venezuela had nationalised its oil and gas industry in the 1970s.

“The illegitimate Maduro regime is using oil from these stolen oil fields to finance themselves, drug terrorism, human trafficking, murder and kidnapping,” the US president said.

For these reasons, the US was designating the Maduro government as a Foreign Terrorist Organisation, Trump said, adding that he was ordering a “total and complete blockade of all sanctioned oil tankers going into, and out of, Venezuela”.

The US, Canada and several European countries do not recognise Maduro as the Venezuelan president. The countries have for long backed the Venezuelan Opposition.

While Venezuelan oil has faced US sanctions for more than a decade, Caracas has circumvented the measures by selling oil at discounted rates in the black market.

On Tuesday, the Maduro government said that Trump’s actions were aimed at “stealing the riches that belong to our homeland”, AFP reported.

Tensions have escalated in recent weeks after Trump signalled his intention to launch military action inside Venezuela.

On November 30, the US president had unilaterally announced that the Venezuelan airspace should be considered closed. On December 10, the US military seized an oil tanker off the Venezuelan coast, claiming that the vessel was transporting sanctioned oil from Venezuela and Iran.

The US’ military deployment in the Caribbean, meant to combat drug trafficking, includes the country’s largest aircraft carrier strike group USS Gerald R Ford and the advanced F-35 fighter jets.