Israeli Defense Minister Ehud Barak has pledged to upgrade his country's defense links with Greece and is reported to have signed a defense cooperation pact with Greek Cypriots to counter Turkish threats against joint exploration of gas fields in the eastern Mediterranean.

Israel's emerging military ties with Athens and the Greek Cypriot government in Nicosia stem in part from the rupture of its strategic alliance with Turkey, Greece's historical foe, that climaxed in May 2010.

But the shifting relationships also reflect the common interest shared by Israel, Cyprus and Greece in exploring and exploiting the vast natural gas reserves that lie deep under the Mediterranean seabed that will transform their economies for decades to come.

Threats abound, however. Lebanon, which also seeks to benefit from the energy wealth under the sea, claims Israel is poaching on its territorial zone, which has not been demarcated by treaty.

The Iranian-backed Hezbollah, currently the dominant partner in the Beirut government, has vowed it will never allow Israel to "plunder" Lebanese assets.

Israel has pledged to use military force to protect its newfound energy wealth.

Israel and Cyprus plan to jointly funnel their gas exports through an underwater pipeline running from the Jewish state through Cyprus to the European Union via Greece.

This infuriates Turkey, which has become bitterly anti-Israeli.

Israel thus wants a more binding defense relationship with the mainland and Cypriot Greeks to protect its gas exports, which could earn it billions of dollars over the next two or three decades.

Barak said when he visited Athens this week that relations with Greece "have never been so close." The two countries held joint air force exercises recently.

Debt-ridden Greece, whose links with Israel were cool for decades, is only too happy to hook up a war-seasoned military power like the Jewish state to confound the Turks amid dramatic changes in the Middle East -- although Greek Defense Minister Dimitris Avramopoulos insisted the new alliance "is not aimed at anyone."

Cypriot Defense Minister Demetris Eliades visited Israel to sign a defense cooperation pact Monday. Cyprus has no navy or air force, so it wants Israel to act as a deterrent to Turkey.

No details were officially disclosed, but Eliades made it clear the Israelis had approval "in advance" to operate in Cypriot air space and waters.

Greek Cypriot sources said Israel had asked to use the Andreas Papandreou air base in Paphos, in the southwestern tip of the island and once used by the Greek air force.

There has been no official word that had been approved, but basing Israeli aircraft in southern Cyprus is guaranteed to rile the Turks.

Turkey, which has occupied the northern third of Cyprus since invading in 1974, insists the majority Greek Cypriots, who rule in the south of the island, cannot unilaterally conduct exploration.

Ankara has launched its own exploration program in waters claimed by Turkish-held northern Cyprus, protected by the Turkish navy and a squadron of F-16 fighters deployed in northern Cyprus in 2011.

Turkey has said it hopes to conclude an exploration deal between the state-owned TPAO oil and gas company with Royal Dutch Shell off the southern coastal city of Antalya.

This exploration program, if it gets going, will be particularly significant for Turkey, which depends on energy imports. Its import bill for 2011 is expected to total $50 billion, two-thirds of its current account deficit.

In 2010, the U.S. Geological Survey estimated the eastern Mediterranean zone, known as the Levant Basin, could contain 122 tcf of gas as well as several billion barrels of oil.

The problem for Turkey is that its war-conquered Cypriot enclave, known as the Turkish Republic of Northern Cyprus, is not recognized by anyone except Ankara. The Nicosia government is universally recognized.

Turkey also has limited maritime territory, in part because many of the Greek islands lie close to the Turkish coast.

Israel hit pay dirt in 2009-10. First was the Tamar field with 8 trillion cubic feet of gas, followed by Leviathan containing an estimated 16 tcf.

Leviathan is believed to extend into Cypriot waters. Indeed, Texas-based Nobel Energy, which made the Israeli strikes, is now drilling in the southernmost of Cyprus' 12 exploration blocks and says it's found reserves of at least 7 tcf -- and counting.