ISTANBUL- Turkey dismissed prospects of any imminent ceasefire in Libya on Monday, saying any deal incorporating the conflict's existing frontlines would not benefit the Ankara-backed Government of National Accord.

In an interview with state broadcaster TRT Haber, Foreign Minister Mevlut Cavusoglu said that the coastal city of Sirte and Jufra air base need to be turned over to the GNA before it agrees to a ceasefire.

Khalifa Haftar's eastern-based Libyan National Army (LNA) has been on the back foot after Turkish support helped the GNA turn back his 14-month assault on the capital Tripoli.

Asked about a possible operation against LNA-held Sirte, Cavusoglu said there was a diplomatic effort to solve the issue.

"There are preparations for an operation but we are trying the (negotiation) table. If there is no withdrawal, there is already a military preparation, they (GNA) will show all determination here," he said.

Turkey's presidency said President Tayyip Erdogan spoke by phone on Monday with Russia's President Vladimir Putin. The two men discussed the war in Libya and in Syria, where they back rival sides, it said, without giving details.

Turkey and the GNA signed a maritime delimitation deal last year, which Ankara says creates an exclusive economic zone from its southern coast to Libya's northeast coast, and protects rights to resources in the eastern Mediterranean.

Turkish Energy Minister Fatih Donmez said in May that Turkish Petroleum (TPAO), which had applied for an exploration permit in the eastern Mediterranean, may begin oil exploration in the region in three or four months. 

Cavusoglu said on Monday that Turkey would start seismic research and drilling operations for natural resources in the part of the eastern Mediterranean covered by the agreement. He did not provide a timeframe.

He added that Turkey was open to sharing with companies from third countries such Italy, the United Kingdom, the United States and Russia.

(Reporting by Ali Kucukgocmen Editing by Dominic Evans) ((ali.kucukgocmen@thomsonreuters.com , @alikucukgocmen; +902123507067; Reuters Messaging: Reuters Messaging: ali.kucukgocmen.thomsonreuters.com@reuters.net))