On Sunday, Turkey's government warned ExxonMobil that its ongoing exploration activity in Cyprus' EEZ could affect regional stability, and it asserted that Turkey will soon begin its own drilling campaign in waters claimed by Turkish Cyprus.

“We have warned the Greek Cypriot administration to stop the unilateral exploration for hydrocarbons in the Eastern Mediterranean," Ankara warned in a statement. “We reiterate our warning to the companies involved in these unilateral exploration and drilling. We remind them that sharing the natural resources of the island of Cyprus relates to the core of the Cyprus issue.”

Turkey cautioned Exxon that drilling in a Cypriot-administered lease block "does not contribute to the stability of the country . . . and may change specific and delicate balances in relation to resolving the Cyprus issue."

Cyprus is divided in two, with the southern half (the Republic of Cyprus) aligned with Greece and the northern half (the Turkish Republic of Northern Cyprus) aligned with Turkey. Both nations are NATO allies, but the administration of Cyprus has been a source of tension between them since the 1970s, when they fought a war over its control. The two Cypriot governments have overlapping EEZ claims, and Turkey asserts that the Turkish Republic of Northern Cyprus has a right to share in the rewards of offshore exploration.

The stakes involved in the ownership of Cyprus' offshore reserves are significant. In February, Eni found a new gas deposit off Cyprus which may hold as much as the giant Zohr field, a 30 trillion cubic foot formation located in Egypt's EEZ.

In a recent interview, Exxon SVP Neil Chapman said that the sovereignty dispute is solely a question for the nations involved. “We are a commercial entity and our business is about producing and developing natural resources on behalf of governments. Any government issues, that’s for governments to discuss and resolve,” he said.

Turkey has shown determination to assert its regional claims. In February, Turkish warships obstructed the navigation of the Italian drillship Saipem 12000 in order to prevent her from exploring a lease block licensed by the Republic of Cyprus. Later that month, charterer and leaseholder Eni abandoned its work at the block.