ISTANBUL, Sept. 14 (Xinhua) -- Senior officials of Turkey, Russia, Germany and France met in Istanbul on Friday, as global and regional powers are wrestling over how best to deal with rebels from their last major stronghold in the Syrian province of Idlib.

Russian presidential aide Yuri Ushakov, German chancellor's foreign policy adviser Jan Hecker and French president's diplomatic adviser Philippe Etienne joined the meeting hosted by Turkish presidential advisor Ibrahim Kalin, Turkey's state-run broadcaster TRT Haber said.

According to the broadcaster, the main agenda of the meeting, also attended by technical experts from the four states, is setting the program and other details of a summit meeting of leaders of the four countries in the upcoming days.

Earlier in the day, local media reported that Turkish President Recep Tayyip Erdogan would meet his Russian counterpart Vladimir Putin on Monday over Idlib in Russia's sea resort city of Sochi.

Now hosting over 3.5 million Syrian refugees on its soil, Turkey fears that a military offensive against Idlib by the Syrian army and its allies, namely Russian and Iranian forces, would trigger another mass flow of refugees into its border and pose fresh threat to its security.

Turkey is trying all it can to thwart an assault on Idlib, an effort being supported by its Western allies.