ANKARA (Reuters) – Russia and Turkey postponed talks on defusing fighting in Libya due to discord over the Ankara-backed Tripoli government’s push to retake the key coastal city of Sirte from Russian-backed eastern forces, a Turkish official said on Monday.

With Turkish military support, Libya’s internationally-recognised Government of National Accord (GNA) has advanced for weeks against Khalifa Haftar’s Libyan National Army (LNA), which is backed by Russia, the United Arab Emirates and Egypt.

Heavy clashes have emerged as the GNA has laid siege to LNA-held Sirte, close to major energy export terminals on the Mediterranean seaboard.

While Russian Foreign Minister Sergei Lavrov did not make the trip to Istanbul on Sunday for a scheduled meeting with his counterpart Mevlut Cavusoglu, the Turkish official said background talks were continuing at expert level.

“A result was supposed to come out (of the meetings), but that stage could not be reached. There are issues where the two countries are on opposing sides,” the Turkish official said on condition of anonymity.

“One of the main issues for the postponement of the Lavrov visit is the (GNA’s) plan for an operation into Sirte. “Once certain regions were taken as part of the…advances, Sirte emerged as a target.”

The United Nations said last week the warring sides had begun new ceasefire talks in Libya after GNA forces repelled a protracted LNA assault on the capital Tripoli.