WASHINGTON - US President Donald Trump on Wednesday demanded Venezuela return assets that he accused the oil-rich South American country took from US oil companies years ago.

"They took our oil rights -- we had a lot of oil there. As you know they threw our companies out, and we want it back," Trump told reporters in the White House, referring to Venezuela's nationalization of its oil sector in the 1970s and under President Nicolas Maduro and his predecessor Hugo Chavez.

In a social media post, Stephen Miller, Trump's deputy chief of staff, on Wednesday described Venezuela's nationalization of its oil industry as "the largest recorded theft of American wealth and property."

"These pillaged assets were then used to fund terrorism and flood our streets with killers, mercenaries and drugs," Miller claimed.

One day earlier, Trump ordered "a total, complete blockade of all sanctioned oil tankers going into and out of Venezuela," stepping up a months-long pressure campaign against the Venezuelan president.

The United States "will not allow a Hostile Regime to take our Oil, Land, or any other Assets, all of which must be returned to the United States, IMMEDIATELY," Trump wrote on the social media platform Truth Social on Tuesday.

The president also announced in the post that "the Venezuelan Regime has been designated a FOREIGN TERRORIST ORGANIZATION (FTO)." However, as of Wednesday evening, there was no change to the Trump administration's FTO list.

The Pentagon seized an oil tanker near Venezuela's coast last week and ordered it to sail to a US port. The White House later confirmed plans to retain the oil, a move Venezuela condemned as "piracy".

Venezuela, a major oil producer, holds some of the world's largest proven oil reserves, though US imports of its crude have fallen sharply over the past decade due to sanctions and political tensions.

US oil major Chevron, operating in Venezuela under a government waiver, says its operations have not been disrupted.

For almost four months, the United States has maintained a significant military presence in the Caribbean, much of it off Venezuela's coast, purportedly to combat drug trafficking -- a claim Venezuela has rejected, calling it a pretext for forcing regime change.

Since early September, US forces have sunk at least 25 alleged drug-trafficking vessels in the Caribbean and eastern Pacific, killing at least 95 people aboard.

While the White House says the military actions target the drug-smuggling into the United States, US Drug Enforcement Administration data show Venezuela is not a major source of drugs entering the country.

A Quinnipiac University poll released Wednesday shows 63 percent of US adults oppose the Trump administration's military attacks on Venezuela, compared with 25 percent who support them.