Four vessels transporting Iranian gasoline headed for Venezuela were seized by the United States in an unprecedented action made by the Trump administration that has the possibility of disrupting the world's oil trade if the Islamic Republic carries out retaliatory measures.

On Friday, the U.S. Department of Justice officials said they held the four oil tankers sent by Tehran to Venezuela, linking the cargo to the country's Revolutionary Guards as it turns up the heat on the two heavily-sanctioned countries.

In a statement, the U.S. said the ships were loaded with more than a 1 million barrels of fuel, adding that the exact location of the vessels could not be determined when they were held because they deactivated their satellite-monitoring device to avoid detection, Bloomberg reported.

U.S. government prosecutors filed a civil forfeiture complaint in Washington in July claiming that the shipment was prepared by Mahmoud Madanipour, a businessman connected to Tehran's Revolutionary Guard Corps, a military branch of Iran listed by Washington as a foreign terrorist group.

An official Iranian envoy to Venezuela said that neither the oil tankers nor their owners were Iranian. A U.S. judge released a warrant for the full seizure of the shipment from the four ships after Washington filed a lawsuit last month.

According to U.S. Justice Department officials, the Iranian Navy tried to board an unrelated oil tanker in what they described as an "apparent attempt" to recover the seized cargo after the seizure, but failed.

These latest move by the U.S. represent its biggest-ever capture of petroleum shipments from Iran, the DOJ statement disclosed, adding the Revolutionary Guards were behind the shipment. No military force was applied in the seizures, a senior U.S. official said.

Asked about the seized fuel during a media briefing at the White House, U.S. President Donald Trump said that Iran is "not supposed to be doing that." The shipment, Trump said will be moved to Houston. With help from its foreign partners, U.S. officials said the seized cargo is now in American custody.

Hojad Soltani, Iran's envoy to Venezuela, said the Trump's labeling of the Guards as terrorists is "another lie and psychological warfare" that Washington has fabricated. The "terrorist #Trump," Soltani claims, cannot recompense his humiliation by Tehran resorting to bogus propaganda.

Frictions between the U.S. and Iran have worsened since Washington backed out of a landmark nuclear agreement in 2018. The Trump administration has implemented broad sanctions on both Venezuela and Iran to block oil exports.