ATHENS — Sanctions by the United States on Turkey for buying a Russian-made S-400 missile system were welcomed by Greece, which could have faced it in a conflict, the act coming after the European Union deferred penalties for Turkey drilling for energy off Cyprus and planning the same off Greek islands.

US President Donald Trump, who is close with Turkey’s authoritarian President Recep Tayyip Erdogan, didn’t want the sanctions, after Turkey was also blocked from buying US F-35 fighter jets because of the Russian buy.

The S-400 also undermines NATO, the defense alliance to which the US, Greece and Turkey belong and the American move was against an ally after the EU didn’t want to antagonize Erdogan.

The EU resistance to sanctions called for by Greek Prime Minister and New Democracy leader Kyriakos Mitsotakis – who had withdrawn them in October to give diplomacy a chance, which failed – was led by Germany, a major arms supplier to Turkey and home to 2.774 million people of Turkish origin.

But Spain, Italy and Greece’s supposed ally France also refused to go against Turkey, reportedly expecting incoming US President Joe Biden to take a tougher line with Erdogan.

"Greece, a member-state of NATO, is observing with satisfaction today's announcement of the US Department of Treasury related to sanctions against the Turkish Republic's Directorate of Defense Industry, the directorate's president, as well as other officials, in application of Section 231 of the Countering America’s Adversaries Through Sanctions Act (CAATSA)," the Greek Foreign Ministry said in a press release.

The move included Turkey's Defence Industries Directorate (SSB) drew fire from Turkey and was expected to put a further strain on Erdogan’s relations with  Western allies, Reuters reported earlier.

The US decision was also based on Turkish actions in Syria, the conflict between Armenia and Azerbaijan and in the Eastern Mediterranean where Turkey had positioned an energy research vessel and warships off the Greek island of Kastellorizo before pulling them back for now.

The sanctions, which were required under a 2017 U.S. law aimed at pushing back on Russia if the Administration found cause, add another element of uncertainty to the relationship as Trump winds down his term. The move is the first time that CAATSA has been used to penalize a US ally.

“The United States made clear to Turkey at the highest levels and on numerous occasions that its purchase of the S-400 system would endanger the security of U.S. military technology and personnel and provide substantial funds to Russia’s defense sector, as well as Russian access to the Turkish armed forces and defense industry,” Secretary of State Mike Pompeo said.

“Turkey nevertheless decided to move ahead with the procurement and testing of the S-400, despite the availability of alternative, NATO-interoperable systems to meet its defense requirements,” he said in a statement.

Turkey’s Foreign Ministry’s statement said that, “Turkey will take the necessary steps against this decision, which will inevitably affect our relations in a negative way, and reciprocate in a way and time it sees fit.”

Russian Foreign Minister Sergei Lavrov, meanwhile, said the sanctions were evidence of American “arrogance" and would hurt the US standing internationally.

Coming weeks before Biden assumes office, the sanctions pose a potential dilemma for his administration, although his team has signaled it is opposed to Turkey's use of the S-400 and the disunity within NATO that it may cause.

(Material from the Associated Press was used in this report)