That escalation on Friday came on the heels of a large-scale US military buildup in the southern Caribbean as President Donald Trump campaigns to oust Venezuelan leader Nicolas Maduro, pushing relations to their most volatile point in years.
The effects could ripple through the region, with Venezuelan oil exports falling sharply and crisis-stricken Cuba, already straining to power its grid, at risk of losing supply.
The US seizure of the Skipper tanker off Venezuela's coast on Wednesday marked the first US capture of Venezuelan oil cargo since sanctions were imposed in 2019.
The vessel is now heading to Houston, where it will offload its cargo onto smaller ships, Reuters reported.
The Trump administration does not recognise Maduro, in power since 2013, as Venezuela's legitimate leader. Washington has signalled more seizures are planned as part of efforts to choke off sanctioned oil flows, and subsequently imposed new sanctions on three nephews of Maduro's wife and six tankers linked to them.
The US military presence in the Caribbean has grown as Trump in recent weeks has discussed potential military intervention in Venezuela, based on accusations that the country ships narcotics to the United States.
The Venezuelan government has denied the accusations. So far there have been more than 20 US military strikes in the Caribbean and Pacific against suspected drug vessels this year, in which nearly 90 people have been killed, alarming human rights advocates and stirring debate among US lawmakers.
While many Republicans have backed the campaign, Democrats have questioned whether the campaign is illegal and urged more transparency, including the release of a full, unedited video of strikes on a suspected drug-trafficking boat.
Machado defied a decade-long travel ban and a period in hiding to travel to Oslo on Thursday, noting that she would soon bring the Nobel Peace Prize back home to Venezuela.
She said Maduro would leave power "whether there is a negotiated changeover or not," vowed she is focused on a peaceful transition, and thanked Trump for his "decisive support".
Machado is aligned with US hardliners who accuse Maduro of ties to criminal networks - claims that US intelligence has reportedly questioned.
When asked at a press conference in Oslo if she believed US intervention was needed in Venezuela, Machado replied, "We are asking the world to help us."
Venezuela condemned the tanker seizure as "blatant theft" and "international piracy," saying it would file complaints with international bodies.
At the same time, Venezuelan lawmakers took a step to withdraw the country from the International Criminal Court, which is currently investigating alleged human rights abuses in the South American country.
Adding to the friction, the Venezuelan government announced the suspension of a US migrant repatriation flight on Friday. A US official countered that deportation flights would continue.
