Ghost fleets are a growing phenomenon, used not just by Venezuela but also by two other oil-producing countries under Western sanctions - Russia and Iran. Financial intelligence firm S&P Global estimates that one in five oil tankers worldwide are used to smuggle oil from sanctioned countries.

The announcement by Trump comes less than a week after the U.S. seized an oil tanker in waters near Venezuela.

Along with the blockade, Trump said he has formally designated Venezuela's Maduro and his government allies a foreign terrorist organization.

Around 12 U.S. warships and 30-50 aircraft positioned off Venezuela highlight the scale of Washington’s military operation.

Venezuelan opposition leader Maria Corina Machado on Friday promised political change after slipping out of the country in secret to collect the Nobel Peace Prize, as the shock waves intensified from the Trump administration's seizure of an oil tanker earlier this week.

While U.S. military pressure on Venezuela has forced vessels to idle at ports or steer away from the region, it continues to be business as usual for one U.S. company. Chevron (CVX), which has been present in Venezuela for more than a century,

Donald Trump alleges Nicolás Maduro's regime is using "stolen oil fields" to fund "drug terrorism". Follow Newsweek's live blog

ANALYSIS — Two words have been missing from the Trump administration’s tough-talking, Navy-deploying policy toward Venezuela: or else. While President Donald Trump and some top aides have expressed deep concerns about Venezuelan President Nicolás Maduro,