Washington DC - The US announced sanctions on four companies Wednesday over their operations in Venezuela's oil sector, in the latest effort to put pressure on the nation's President Nicolas Maduro.

The US Treasury Department also identified four related oil tankers as blocked property.

"These vessels, some of which are part of the shadow fleet serving Venezuela, continue to provide financial resources that fuel Maduro's illegitimate narco-terrorist regime," the Treasury Department charged in a notice.

It warned that parties involved in the Venezuelan oil trade will continue facing "significant sanctions risks."

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"The Treasury Department will continue to implement President (Donald) Trump's campaign of pressure on Maduro's regime," Treasury Secretary Scott Bessent said in a statement.

On Tuesday, Washington unveiled sanctions targeting Iran's drone trade with Venezuela. It blacklisted 10 individuals and entities based in Venezuela and Iran over purchases of Iranian-designed drones, efforts to procure chemicals used for ballistic missiles, and other stated concerns.

The Trump administration has been ramping up pressure on Maduro, who denies US accusations that he runs a drug cartel. Caracas contends that Washington is seeking to overthrow Maduro to seize Venezuela's oil reserves.

Trump has declared a blockade of sanctioned oil vessels sailing to and from the South American country.

In addition to a massive US naval deployment in the Caribbean, US forces have launched at least 30 strikes on boats it claims – without providing proof – are carrying drugs, killing over 100 people.