BRUSSELS: EU countries are struggling to agree what measures to take to punish Turkey for pursuing drilling operations off Cyprus in defiance of repeated warnings, diplomats said Friday.

Nearly three days of talks among ambassadors in Brussels have failed to produce an agreement on what measures to take, highlighting differing views on how to deal with Turkey, a vital but prickly neighbour for the EU.

The discovery of huge gas reserves in the eastern Mediterranean has sparked a dispute between EU member Cyprus and Turkey, which has sent two ships to carry out drilling and vowed to continue.

The EU last month warned Turkey it could face sanctions if it did not cease what the bloc called "illegal" drilling in Cyprus's exclusive economic zone, and diplomats began discussing what measures to impose on Wednesday.

The steps being considered include the halting of high-level talks with Turkey, as well as cuts to pre-accession financial assistance and suspension of talks on an aviation agreement.

Greece and Cyprus are understood to be pushing for sanctions targeting people linked to the drilling operations, while others are keen to strike a more moderate tone.

"We have to look at the larger context: Turkey is a NATO member, the refugee agreement," one EU diplomat said.

"That has to be taken into account, there has to be a balance."

The package of measures is supposed to be agreed by ambassadors before a meeting of foreign ministers on Monday, but if they cannot find consensus it may fall to the ministers themselves to make a decision.

A senior EU official said the bloc was "quite worried" about a second round of Turkish drilling that took place last month.

"This is an issue of clear solidarity with Cyprus -- we want Turkey to suspend this," the official said.

The United States and Egypt joined a chorus of international criticism this week, with Washington urging Turkish authorities to halt the operations.

Ankara says its actions abide by international law and that it is drilling inside its continental shelf. —AFP