Turkish President Tayyip Erdogan said on Wednesday a military operation by his forces to push back a Syrian government offensive against rebels in northwestern Syria is now "a matter of time" after talks with Russia failed to halt the assault.

Turkish troops have already massed inside the Idlib region and more were heading to the border area, bringing NATO members Turkey and Russian-backed Syria close to the brink of direct confrontation.

The Kremlin, which has supported Syrian President Bashar al-Assad's push with air strikes, said a clash between Turkish and Syrian forces would be a "worst-case scenario" and Russia would work to prevent the situation from worsening.

Syrian troops supported by Russian warplanes and special forces have been battling since December to eradicate the last rebel bastions in Idlib and Aleppo provinces in what could be one of the final chapters of the nine-year civil war.

Nearly one million civilians have fled from air strikes and artillery barrages towards the closed frontier, overwhelming relief agencies and alarming Turkey, which already hosts 3.6 million Syrian refugees and says it cannot handle more. 

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Erdogan threatens imminent military operation

Speaking to lawmakers from his ruling AK Party on Wednesday, Erdogan said Turkey was determined to make Idlib a secure zone even while talks with Moscow continued. Several rounds of diplomacy have failed to reach an agreement so far, he said.

"We are entering the last days for the regime to stop its hostility in Idlib. We are making our final warnings," said Erdogan, whose country has the second-largest army in NATO.

"Turkey has made every preparation to carry out its own operational plans. I say that we can come at any point. In other words, the Idlib offensive is only a matter of time."

Erdogan on Saturday appeared to move forward his earlier end-of-February deadline for a Syrian withdrawal from Idlib.

Assad has shown no sign of doing so and has predicted the eventual defeat of his foes. They include Turkish-backed rebels and jihadist militants.

An opposition military source told Reuters that 15,000 Turkish soldiers are now in northwestern Syria after numerous convoys poured into the territory in recent days.

Ankara and Moscow signed an agreement in 2018 to establish a de-escalation zone in Idlib allowing both sides to set up observation posts. Since the escalation in the conflict, both sides have accused each other of flouting the agreement.

(Cover: Turkish President Recep Tayyip Erdogan speaks to journalists at parliament in Ankara, Turkey, February 19, 2020. /AP)