The US seized two sanctioned oil tankers linked to Venezuela in two separate missions in the North Atlantic and the Caribbean.

After a two-week pursuit, US forces boarded the Russian-flagged Marinera – originally known as the Bella 1 – over alleged sanctions violations, in a high-stakes operation that could risk confrontation with the Kremlin after Moscow reportedly dispatched a submarine to safeguard the vessel.

The UK confirmed it provided assistance for the seizure of the Marinera, with the RAF providing extra surveillance and navy refuelling while capture under way. The UK argued the operation was legal and justified because the “stateless” vessel had breached US sanctions on Iran. The UK’s support was “in full compliance with international law”, defence secretary John Healey said.

However, Russia said the seizure had violated maritime law after claiming it had given the vessel permission to fly the Russian flag a month ago.

Meanwhile the US Coast Guard said it had separately intercepted another dark-fleet tanker that is under sanctions, the M Sophia, in a pre-dawn operation in the Caribbean.

The White House press secretary Karoline Leavitt later confirmed that the Marinera crew members were now subject to prosecution and could be transferred to the US “if necessary”.

The Russian foreign ministry demanded the US ensure the humane and dignified treatment of Russian citizens onboard the Marinera and guarantee their swift return to Russia.

Ukraine’s foreign minister said Kyiv welcomed the seizure of the tanker, adding it was a good example of how to act against Moscow and said it showcased “President Trump’s resolute leadership”. “We welcome such an approach to dealing with Russia: act, not fear. This is also relevant to the peace process and bringing a lasting peace closer,” Andrii Sybiha wrote on X.

On Venezuela, the White House also claimed that oil from the country would arrive in the US “very soon”, following Trump’s announcement of a deal with Caracas to get access to up to $2bn worth of Venezuelan crude.

But Venezuela’s state-run oil company PDVSA said that it is progressing in negotiations with the US for oil sales, as a board member for the company told Reuters the US will need to buy cargoes at international prices. “If they want to buy it, they will have it in due time, sold at the international price,” PDVSA board member Wills Rangel told Reuters. “Not the way [Trump] intends, as if that oil belongs to them because we supposedly owe them. We do not owe anything to the United States.”

US secretary of state Marco Rubio told reporters that the US “is not winging it” in Venezuela and that the Trump administration has a long-term plan for the country. The three-step plan for Venezuela that will begin with stabilizing the country after US forces seized Nicolás Maduro on Saturday, overseeing the country’s recovery and finally a transition to a more representative form of government, Rubio told reporters.

Rubio also confirmed he would be meeting with Denmark next week to discuss Greenland.

Leavitt told reporters that the Trump administration was “actively discussing” the purchase of the island and while diplomacy was the first option, “all options are always on the table”. In a statement earlier in the day, Leavitt had added that “utilizing the US military is always an option at the commander-in-chief’s disposal”. She also said told reporters that the US controlling Greenland would deter Russian and Chinese aggression in the Arctic.