This year, as they step up commercial relations to try to rescue their respective oil industries, both of which are under extreme pressure from U.S. sanctions, the shipment is the latest example of collaboration between the two OPEC nations.

2.1 million barrels of Iranian condensate were discharged by the very large crude carrier (VLCC), reported in shipping databases under the name Horse, to be used as a diluent for Venezuela 's extra-heavy oil production in September.

It loaded Merey heavy crude, the flagship grade of Venezuela, for export under an agreement between, according to a PDVSA source, state-run oil companies Petroleos de Venezuela and National Iran Oil Company (NIOC).

As required by international shipping law in most cases, the vessel arrived in Venezuela and loaded crude without transmitting its position until about 2 a.m. (0600 GMT) displayed the Refinitiv Eikon vessel-tracking information on Friday.

The export schedules did not list the destination load of the cargo.

As part of a series of steps to try to overthrow Venezuelan President Nicolas Maduro, the United States has sanctioned PDVSA. To attempt to thwart the country's nuclear program, it has imposed sanctions on Iran's oil industry.

Washington has taken no steps to interrupt the voyage of Master Honey, or a separate flotilla of three Iranian tankers that last week carried fuel to gasoline-starved Venezuela.

Maritime Business World