The United States is increasing pressure on the elusive “shadow fleet” of oil tankers that has helped fund Russia’s war in Ukraine, seizing over half a dozen vessels in Venezuelan waters in recent weeks.
The U.S. blockade of Venezuela and its actions against shadow fleet vessels could be significant for the West as it seeks to disrupt Iran, Russia, and Venezuela’s efforts to evade sanctions and international maritime laws, though it’s still too early to tell how successful the measures will be.
Since the start of December, the Trump administration has seized seven oil tankers that were, or were previously known for, carrying Venezuelan oil.
The seizures began as part of the administration’s campaign to oust former Venezuelan dictator Nicolas Maduro, but have continued as President Donald Trump seeks to rebuild the country’s oil industry and escalate its crackdown on other sanctioned ships known or suspected to be part of a shadow fleet.
The White House is trying to use the leverage given to it via the blockade to force the Venezuelan government, now led by Maduro’s vice president, Delcy Rodriguez, to capitulate to its demands.
There is now speculation as to whether the administration’s actions could lead other vessels within this broader shadow fleet to stop transporting sanctioned oil from countries such as Russia and Iran over fears of being targeted in similar operations.
What is the shadow fleet?
The shadow fleet is the name given to the hundreds, if not thousands, of illegal tankers Iran, Russia, and Venezuela primarily operate while trying to evade Western sanctions and legal requirements.
The exact number of ships currently part of this fleet is unknown, though experts estimate there are roughly 1,000 vessels transporting oil and other commodities in violation of U.S. and other Western sanctions.
These tankers are often older and beyond their expected shelf life. Their crews will frequently try to distort information about their location, activity, where they’re coming from, and their intended port. Even though buying oil from countries in contravention of existing sanctions or international law has legal risks, the oil itself is often cheaper, thus making it attractive to buyers.
“Nefarious operators have several tools in their detection-avoidance toolkit,” such as operating without their automatic identification systems turned on in violation of the International Maritime Organization requirement, Clayton Seigle, a senior fellow in the Energy Security and Climate Change Program at the Center for Strategic and International Studies, told the Washington Examiner.
“Another is ‘spoofing’ their real location by tricking the AIS system into broadcasting a false location, sometimes in another region of the world,” he added. “Other tricks include swapping identities with a different ship, a maritime version of identity theft.”
Russia is considered to be one of the primary culprits using this fleet to get around European Union and U.S. sanctions and continue selling its crude to China and India. Moscow has relied on the revenue from these sales to fuel its yearslong war in Ukraine.
In December, the Centre for Research on Energy and Clean Air estimated that roughly 28% of the 93 identified shadow vessels operating under false flags at the end of the month were carrying Russian crude oil and oil products. The majority of Russian crude oil exports, around 68%, continue to be carried by these sanctioned shadow tankers, CREA found.
Iran has also been heavily accused of utilizing the shadow fleet to get around international sanctions to facilitate oil sales and use the funds for what the Trump administration has described as “destabilizing activities.”
Western crackdown
The shadow fleet began to expand rapidly following Russia’s invasion of Ukraine in February 2022. At the time, the Group of Seven implemented a price cap of $60 a barrel on Russian oil. The idea was to restrict the amount of money Moscow could make through oil sales without creating a dramatic supply shortage in global markets.
While exports of Russian oil and oil products fell, revenue from the exports continued to rise. One likely reason for this was the use of the shadow fleet of tankers to get around the price cap.
With the price cap failing to act as a strong deterrent, the U.S. has taken several steps over the past few years to tighten the sanctions regime.
Former President Joe Biden sought to crack down on Russia’s involvement in the shadow fleet in the final days of his administration, imposing sweeping sanctions on nearly 200 vessels suspected of illegally transporting Russian oil.
Trump moved to increase the pressure on the shadow fleet two months later, targeting Iran.
In February 2025, the Trump administration placed sanctions on more than 30 people and vessels in Iran, the United Arab Emirates, Hong Kong, India, and China, all of which the administration said played a role in helping sell and transport tens of millions of barrels of crude oil from Iran.
At the time, the International Energy Agency warned that the sanctions may not be strong enough to deter the shadow fleet completely, noting that deceptive shipping practices would continue to undermine Western efforts to dismantle illegal shipping.
The Trump administration also later moved to implement secondary sanctions on Moscow, targeting India over its imports of Russian oil products. In August, Trump increased tariffs on India from the previously announced 25% rate to 50% as a penalty for its purchases of Russian crude.
While Treasury Secretary Scott Bessent has claimed that India “geared down and stopped buying Russian oil,” India has not acknowledged such a shift in its imports. Trade data reviewed by Reuters, however, does show that India’s imports of Russian oil fell to their lowest level in two years in December.
Overall, these additional sanctions have seen some success in curbing Russian exports via the shadow fleet, as the Kyiv School of Economics found that Russia’s oil export revenues fell to $11 billion in November of last year, the lowest level since the invasion of Ukraine.
Effect of the seized tankers
The overall U.S. blockade around Venezuela could be significant for the international shadow fleet operation, even though only a handful of tankers have been seized to this point.
Energy analysts believe it sends a signal that the U.S. government is willing to halt the export of sanctioned oil, despite the ramifications for that country’s exports or revenue from crude.
Seigle told the Washington Examiner that the blockade and seizure of the sanctioned Venezuelan oil will likely have the greatest effect on China, whose private refineries have been handling the largest share of the South American country’s crude exports.
China will very likely move to replace these barrels, though at a higher cost, and could look to Russia and Iran.
“If the vessels get hired for other work moving Iranian and Russian barrels, then extra shipping capacity will marginally reduce costs and increase revenues from those sales,” he said.
Seigle noted, though, that the seizure of the ships may cause some of these shadow tankers to leave the business altogether, leading to higher costs and reduced revenues for exporters such as Russia and Iran. One reason vessels may be more inclined to halt their business is that other Western nations may try to implement similar methods of halting the flow of sanctioned oil in their own waters.
“This is absolutely a game changer. Trump has broken the business model for the Dark Fleet in Venezuela,” Michelle Bockmann, a maritime intelligence analyst at Windward, told the Washington Examiner. “He’s provided a template for the EU and the U.K. to deal with a similar threat that they’ve got in their own backyard.”
“There is chatter from the U.K. and the EU about being able to seize and interdict these vessels in their waters, especially those that are falsely flagged,” Bockmann added.
In December, just under half, 46%, of Russian oil was transported by ships flying false flags transiting through the Danish Straits, CREA estimated.
One of the tankers seized this month, the Bella 1, had registered under a Russian flag, and Moscow deployed naval assets to protect it as it attempted to escape the pursuit from the U.S.
Since last June, more than 40 vessels a part of the shadow fleet registered under a Russian flag, an apparent effort to gain protection from Moscow. Since Russia failed to shield Bella 1 from U.S. forces, it is unclear whether the vessels will continue to look to Moscow for safeguarding.
Last May, however, Russia deployed a fighter jet into Estonian airspace as the Estonian navy was trying to escort a tanker from its waters that was heading to the Russian port of Primorsk. The difference between the incidents and Russia’s ability to come to the aid of a shadow tanker being pursued by Western authorities could come down to proximity.
What comes next?
While the Trump administration has seized just about seven sanctioned oil tankers, the U.S. government has plans to interdict many more.
Sources told Reuters last week that the U.S. government filed for court warrants to seize dozens more oil tankers linked to transporting Venezuelan oil. These warrants have been filed in district courts, primarily in Washington, D.C., and would allow the U.S. to continue seizing and confiscating oil cargoes.
It is unclear how many warrants the administration filed, but sources told the outlet that they amounted to “dozens.”
There is some skepticism that the U.S. efforts to seize sanctioned shadow tankers can be implemented elsewhere, particularly as these vessels often travel through highly transited areas crucial to the global transportation of oil, such as the Persian Gulf and the Strait of Hormuz.
Noam Raydan, a senior fellow at the Washington Institute for Near East Policy, told the Washington Examiner that similar operations could result in major disruptions.
“The U.S. policy, in my opinion, towards the shadow fleet in Venezuela might be difficult to apply elsewhere around the world,” Raydan said.
HOW TRUMP’S OIL TANKER SEIZURES FIT IN THE US-VENEZUELA STRATEGY
Seigle also pointed out that there is no “real effort” underway to shut down the shadow fleet on a global scale. While Denmark could attempt to halt transportation via the Danish Straits, he pointed out that the Scandinavian country has chosen not to take such action in the last three years.
Instead, Seigle said, rigorous secondary sanctions on buyers of the sanctioned oil transported by these shadow vessels could continue to have an effect, as well as reducing the oil price cap on Russian oil.
