A U.N. envoy said Wednesday that deadlocked talks to reunify ethnically split Cyprus were at risk of being derailed amid a dispute over rights to search for offshore gas.

Espen Barth Eide said it's unclear when talks would resume.

"I am increasingly concerned that things are not moving," Eide said after talks with Cypriot President Nicos Anastasiades.

Cyprus was divided in 1974 when Turkey invaded after a coup aiming at union with Greece. Turkey doesn't recognize Cyprus as a state and insists it won't allow a unilateral oil and gas search by the internationally recognized Greek Cypriots at the expense of Turkish Cypriots in the island's breakaway north.

A Turkish Cypriot declaration of independence is recognized only by Turkey, which maintains 35,000 troops in the north.

Anastasiades, a Greek Cypriot, suspended talks last October when Turkey announced plans to mount a mineral search in waters where the Cypriot government had licensed companies such as Italy's Eni and South Korean Kogas to drill. A Turkish research vessel has been conducting seismic tests under naval escort there.

Hopes that talks would restart soon were dashed last week when Turkey said it plans to continue seismic tests in the area.

Anastasiades said talks can't resume while Cyprus' sovereign rights are being violated and that Turkish Cypriots can share in any potential gas wealth after a peace deal is reached.

But Anastasiades softened his stance on a key Turkish Cypriot demand, suggesting that mineral-related issues could be discussed once negotiations have reached the final stages.

The move earned plaudits from Eide, but Turkish Foreign Minister Mevlut Cavusoglu said that Greek Cypriots weren't acting in good faith when drilling continues without Turkish Cypriot input.

Cavusoglu said after talks with Turkish Cypriot leader Dervis Eroglu on Wednesday that Turkish Cypriots must have an immediate say in any drilling in order to ensure their rights are safeguarded.