An Iranian tanker under sanctions by the United States and believed headed to Syria – barred by Greece from stopping at the port of Kalamata – reportedly plans to transfer its oil to another vessel in Greek waters, posing a diplomatic problem.

The transfer of some 2.1 million barrels of oil being carried by the Adrian Darya 1 to another vessel is possible, weather permitting, according to analysts, said Kathimerini, although it would put new Prime Minister Kyriakos Mitsotakis in an awkward position.

Relations between Greece and the United States hit an apogee, ironically, under the former ruling Radical Left SYRIZA that had been anti-American before then-Premier Alexis Tsipras changed his tune and welcomed a bigger US military presence in the country after saying he would stop it.

Shipping Minister Yiannis Plakiotakis told SKAI TV that Greek authorities had received no formal docking request by the Adrian Darya 1, which, according to shipping tracking data, was scheduled to reach Kalamata on Aug. 25 before being prohibited.

Diplomatic sources who weren’t named by the paper said that the Greek Foreign Ministry was “closely monitoring the issue” and was in contact with the US “via diplomatic channels,” code language to indicate the US won’t tolerate the ship being used in Greek waters.

But there was no explanation as to why the US, which has a naval base on the island of Crete on Souda Bay, didn’t send a warship to seize it with the State Department saying vaguely that it had a “strong position.”

Any efforts to assist the tanker could be viewed as providing material support to a US-designated foreign terrorist organization, the official said, a stance backed by an unnamed US Embassy official who said if Greece allows the Iranian ship to do anything that gets around the sanctions it would carry heavy consequences.

The US has given the same warning to any other country in the Mediterreanean. The ship had been in detention on the British territory of Gibraltar after being seized by Royal Marines but was let go because Iran seized a British ship as a hostage.

The US said that the revenues from oil would go to Iran’s Islamic Revolutionary Guard Corps, considered a terrorist group by Washington, with tensions ratcheting up again between the countries to near-conflict levels.