US Secretary of State Mike Pompeo's decision to visit Greece was reportedl cemented when Turkey used a Russian-made defense system to light up US-made Greek F-16 fighter jets after an exercise off Cyprus.

Turkey went ahead with the purchase of the S-400 missile defense system even though Russia is an ideological enemy of NATO, the defense system to which Greece, Turkey and the US belong.

Turkey was allowed to go ahead with the buy undeterred by NATO, even though the S-400 could compromise the defense alliance's own weapons and defenses, and as Turkey repeatedly violated Greek airspace and waters.

The US barred Turkey from buying American-made F-35 fighter jets as a result but the use of the S-400 radar to detect the Greek fighter jets irked the US and sent Pompeo to Greece, said Kathimerini.

He was in the country to back Greece against Turkey planning to drill for oil and gas off Greek islands, and Turkey withdrew an energy research vessel and warships from near the Greek island of Kastellorizo.

Facing the possibility of sanctions from the European Union, Turkish President Recep Tayyip Erdogan agreed to host talks in Ankara with Greek officials, not come to Athens despite Greece claiming Turkey was going to violate Greek waters.

Turkey apparently activated the S-400 to pinpoint the Greek fighter jets as they were returning from the Eunomia exercise on Aug. 27 from Cyprus, where Turkey is also drilling for oil and gas in Cypriot waters.

The alleged use of the radar system was set to set off alarm bells in Washington, the paper said, over Turkey going ahead with testing, which could lead to sanctions from the US as well although Erdogan is a favorite of President Donald Trump.

After the US partially lifted an arms embargo on the legitimate government of Cyprus – Turkey has occupied the northern third since an unlawful 1974 invasion – Pompeo went to the island on Sept. 12 and Greece from Sept. 27-29.

According to reports from a section of the Turkish opposition media, a test of the S-400 systems is planned by Ankara near Sinop on the Black Sea, upset that Pompeo went to Greece.

The US, which renewed a military cooperation deal with Greece, where the US Navy has a base at Souda Bay on Crete, also permanently moored the expeditionary sea base the  USS Hershel “Woody” Williams there, another bulwark against potential Turkish provocations in the region.

The support of a 106,000-ton displacement ship capable of carrying helicopters, drones and other systems requires significant changes to the base, which is in the area where Turkey plans to drill in Greek waters.