On Tuesday, the US military's Southern Command posted on social media that it "remains ready to support our US government agency partners in standing against sanctioned vessels and actors transiting through this region.

"Our sea services are vigilant, agile, and postured to track vessels of interest. When the call comes, we will be there."

Before any US military operation was launched from the UK, Washington would be expected to inform its ally.

For now, the UK Ministry of Defence says it will not comment on other nations' military activities.

The US officials quoted by CBS suggested that America could mount an operation like one conducted last month when US forces seized the Skipper, a large crude oil tanker, flagged to Guyana, that had just left port in Venezuela.

Under international law, vessels flying a country's flag are under the protection of that nation. However, simply changing a ship's name and flag doesn't necessarily change much, Dimitris Ampatzidis, senior risk and compliance analyst at maritime intelligence firm Kpler, told BBC Verify.

"US action is driven by the vessel's underlying identity [IMO number], ownership/control networks, and sanctions history, not by its painted markings or flag claim," he said.

Michelle Bockmann, a maritime intelligence analyst at Windward, said changing to a Russian registry could "complicate US enforcement efforts".

"Under the UN Convention of the Law of the Sea, there's a provision that allows a stateless vessel to be boarded by authorities. By reflagging to Russia, the vessel is no longer able to be boarded under this provision," she explained.

Bockmann adds that she has previously observed vessels changing their flag mid-voyage, but "it's highly unusual and only seen with dark fleet tankers".

The potential stand-off over the oil tanker comes days after the US shocked the world with the arrest of Venezuela's Nicolás Maduro in Caracas. It bombarded targets in the city during the operation to extricate him and his wife on suspicion of weapon and drug offences.

Since he was seized, BBC Verify has identified three US-sanctioned tankers that have switched to a Russian registry, including the Marinera.

This follows a broader trend.

Since the seizure of the Skipper, BBC Verify has identified 19 US-sanctioned oil tankers that have switched to a Russian registry, with many of them having previously sailed under a false flag.