(Bloomberg) -- Turkey warned Greece against exceeding limits on military forces allowed on Greek islands in the Aegean Sea, as the US urged the NATO allies to step back from a recent escalation in tensions.

“We are extremely serious, we are not bluffing,” Turkey’s Foreign Minister Mevlut Cavusoglu told Hurriyet newspaper in an interview published Thursday. 

Greece must comply with a 1947 peace treaty that allows only a small contingent of Greek soldiers on the Dodecanese islands or “we will take this matter” further, Cavusoglu said without elaborating. He spoke on his return to Turkey from Israel late Wednesday.  

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The Dodecanese -- a group of islands off the Turkish coast including Rhodes and Kos -- were ceded to Greece by Italy following World War II.

​Strains over contested territorial waters are mounting steadily as longtime rivals Greece and Turkey -- which went to war over now divided Cyprus in 1974 -- search for energy in the eastern section of the Mediterranean, which has yielded substantial natural gas discoveries in recent years for Israel, Cyprus and Egypt. 

In a letter to the United Nations on Wednesday, Greece called on Turkey to stop questioning Greece’s sovereignty over its Aegean islands, particularly through “legally baseless and historically false assertions” and to abstain from threatening Greece with war in case it extends its territorial waters. 

Greece said it “continues to firmly believe that the two countries can resolve their outstanding difference, namely the delimitation of their continental shelves and exclusive economic zones.”

Turkish President Recep Tayyip Erdogan met with Greek Prime Minister Kyriakos Mitsotakis in Istanbul in March but those talks didn’t provide a breakthrough. 

Earlier this week Erdogan accused Mitsotakis of seeking to block the sale of US F-16 fighter jets to Turkey during the Greek leader’s visit to Washington.

Turkey also says there has been a shift in US policy in favor of Greece in territorial conflicts between the two countries, and increasing US military access to bases in Greece.  

“We see a deviation in this balance and told this to Blinken,” Cavusoglu said referring to his May 18 meeting with US Secretary of State Antony Blinken in New York. 

The US called on the NATO allies “to work together to maintain peace and security in the region and to resolve their differences diplomatically,” State Department spokesman Ned Price said Wednesday. “We also encourage them to avoid rhetoric that could further raise tensions.”

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The flare-up comes as NATO tries to overcome Ankara’s opposition to the admission of Sweden and Finland into the military alliance. Ankara alleges the Nordic nations support autonomy-seeking Kurdish militants who’ve been battling Turkey for years.

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