The appearance of the Adrian Darya-1 in waters near Tartus comes as Iran was prepared to Saturday to announce what further steps it had taken to move away from its 2015 nuclear deal with world powers, more than a year after President Donald Trump withdrew the U.S. from the accord.
Both events have raised tensions between Iran and the U.S. over recent months that have seen mysterious attacks on oil tankers near the Strait of Hormuz, Iran shooting down a U.S. military surveillance drone and other incidents across the wider Middle East. The U.S. issued a new warning of a potential threat to shipping off of Yemen early Saturday.
The tanker Adrian Darya-1, formerly known as the Grace-1, turned off its Automatic Identification System late Monday, leading to speculation it would be heading to Syria. Other Iranian oil tankers have similarly turned off their tracking beacons in the area, with analysts saying they believe crude oil ends up in Syria in support of embattled President Bashar Assad's government.
Images obtained by The Associated Press early Saturday from Maxar Technologies appeared to show the vessel off Syria's coast, some 2 nautical miles (3.7 kilometers) off shore under intermittent cloud cover.
Iranian and Syrian officials have not acknowledged the vessel's presence there. There was no immediate report in Iranian state media about the ship, though authorities earlier said the 2.1 million barrels of crude oil onboard had been sold to an unnamed buyer.
The oil on board would be worth about $130 million on the global market, but it remains unclear who would buy the oil as they'd face the threat of U.S. sanctions.
The new images matched a black-and-white image earlier tweeted by John Bolton, the U.S. national security adviser.
"Anyone who said the Adrian Darya-1 wasn't headed to #Syria is in denial," Bolton tweeted. "We can talk, but #Iran's not getting any sanctions relief until it stops lying and spreading terror!"
U.S. prosecutors in federal court allege the Adrian Darya's owner is Iran's paramilitary Revolutionary Guard, which answers only to Supreme Leader Ayatollah Ali Khamenei. On Wednesday, the U.S. imposed new sanctions on an oil shipping network it alleged had ties to the Guard and offered up to $15 million for anyone with information that disrupts the Guard's operations.
Brian Hook, the U.S. special envoy for Iran, also has reportedly emailed or texted captains of Iranian oil tankers, trying to scare them into not delivering their cargo.
Meanwhile Saturday, the U.S. Transportation Department's Maritime Administration issued a new warning to shippers about a potential threat off the coast of Yemen in the southern Red Sea.
"A maritime threat has been reported in the Red Sea in the vicinity of Yemen," the warning read. "The nature of the event is potential increased hostilities that threaten maritime security."
The capital and areas of war-torn Yemen remain held by the country's Houthi rebels, which are allied to Iran. Shipping in the Red Sea has been targeted previously by rebel attacks. On Wednesday, a warning went out after two small boats followed one ship in the region, but there's been no other information about a new threat there.
Cmdr. Joshua Frey, a spokesman for the U.S. Navy's Bahrain-based 5th Fleet, said the Navy remained ready to maintain the safety of shippers in the region. He declined to specifically discuss the warning. The U.S. military's Central Command did not respond to a request for comment.