Tension over disputed natural gas fields in the eastern Mediterranean has sharpened in recent days with Turkey sending a second exploration ship to Cyprus while Israel, feuding with Turkey, has air force exercises.

The Israeli government has demanded oil and gas companies accelerate offshore drilling programs to hasten production at two major gas fields, Leviathan and Tamar, which are said to contain 25 trillion cubic feet of gas.

The exploration zones off southern Cyprus adjoin the Israeli fields and there's speculation these could be larger than Leviathan and Tamar.

Together these potentially vast fields could transform the eastern Mediterranean, long deprived of energy resources, into a strategically important region -- but one riven by geopolitical rivalries and seemingly perpetual conflict.

"What we're seeing now is a redrawing of the strategic terrain in the eastern Mediterranean," said James Ker-Lindsay, a specialist in Turkey and Cyprus at the London School of Economics.

The U.S. Geological Survey reported in 2010 that the Levant Basin, which covers waters off Syria, Lebanon, Israel and Cyprus, contains 122 trillion cubic feet of natural gas, plus up to 4 billion barrels of oil.

Any confrontation triggered by the drive to exploit these reserves "would pretty much close Turkish hopes of became a European Union member," Ker-Lindsay noted.

The discovery of gas off Israel, and expectations that similar reserves lie in Lebanese and Cypriot maritime exclusion zones, has complicated an already complex security crisis in the region and threatens to widen it.

The multi-sided gas dispute, with Lebanon claiming Israel's Leviathan field extends into its waters, intersects with the 63-year-old Arab-Israeli conflict and the age-old rivalry between Greece and Turkey.

Turkey, a firm military ally of Israel until 2010, is locked in a bitter dispute with the Jewish state.

Turkey under the Islamic Justice and Development Party headed by Prime Minister Recep Tayyip Erdogan is bent on re-establishing the country as the region's paramount power as it was during the Ottoman era.

Ankara is now aligned with the Arab and Muslim world, pushing Israel into boosting its links with Greece -- and joining with the Greek Cypriots to jointly develop their adjacent gas fields.

The plan is to export the gas through undersea pipelines running from Israel, through Cyprus to Greece and into the energy-hungry EU. Turkey would be left out in the cold.

Houston's Noble Energy Co., which hit pay dirt off Israel, is also exploring in Cypriot waters and is confident Leviathan extends into Cyprus's zone.

Tensions have been running high for some time and seem to be increasing by the week.

Turkish Energy Minister Taner Yildiz said the new exploration ship being sent in by Ankara will prospect for gas and oil off the south coast of Cyprus. It will join another Turkish vessel, the Piri Reis, which has been conducting exploratory work in the same waters since mid-September.

Yildiz said a third exploration ship was in the region but gave no details.

"The gas exploration will continue in the north and south and even off the western parts of the island," he declared.

Cyprus has been divided since Turkey invaded the island off its southern coast in 1974 after a short-lived Athens-engineered coup by supporters of union with Greece. Turkish forces seized the northern one-third of the island and proclaimed it the Turkish Republic of Northern Cyprus.

It's recognized only by Ankara; the Greek Cypriot government in Nicosia is recognized internationally.

In September, the Greek Cypriots initiated drilling operations in the southernmost of the 12 exploration blocks in their waters.

Turkey, which has threatened to send in its navy, says Nicosia has no right to drill while United Nations-backed negotiations to reunify the island drag on. These have failed to find a settlement for the last two decades.

Ankara swiftly challenged the Greek Cypriots by sending in the Piri Reis, escorted by a Turkish navy corvette and F-16 fighter jets deployed in the TRNC, where some 40,000 Turkish troops are stationed.

Now there's talk of Israel joining the Greek Cypriots in a military alliance. An Israeli official insisted the recent air exercises in Cypriot airspace were routine, with "no political agenda."

But in the current tense climate, it's doubtful Ankara will see it that way.