update2: A top Turkish official warns of bigger escalation now that Syrian Army units appear to be heading to besieged Kurdish towns along the border with Turkey.

Erdogan aide Yasin Aktay has said "conflict between the two armies" is likely if pro-Assad forces enter the northeast region which has now been abandoned by US troops.

#Erdogan's adviser Yasin Aktay spoke to the Russian news agency Sputnik Arabic:



"If the Syrian Army tries to enter the northeast of #Syria, #Turkey will resist. It may come to a conflict between the two armies." — Ali Özkök (@Ozkok_A) October 13, 2019

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update: It's official, after what appears a major deal between the Kurdish-led SDF and Damascus was struck in the wake of a US exit from the region:

"Syrian military forces will be deployed on the border with Turkey by tomorrow morning in certain areas," reports Danny Makki, a well-known war correspondent in Damascus.

This as multiple videos have spread online showing pro-Damascus forces entering Manbij:

#Update: Also another video of this Syrian Arab Army #SAA convoy advancing near into #Manbij with tanks also spotted in this convoy to help #SDF and #YPG forces drive the Turkish aggression out of #Syria. #Turkey pic.twitter.com/71CXAzZY2O — Sotiri Dimpinoudis (@sotiridi) October 13, 2019

Erdogan has reportedly vowed that pro-Turkish forces will continue their advance despite the Syrian Army apparently coming to the defense of besieged Kurdish forces.

What we know so far about Syrian army deployment in N. #Syria so far#Manbej #Kobani#Shiekhmaqsoud

All to be entered this evening #Qamishly #Hasakeh



Reports of gradual control within 48 hours — Danny Makki (@Dannymakkisyria) October 13, 2019

It's as yet unclear what the Russian military's role in supporting its Syrian ally will be; however, we could be witnessing the beginnings of Putin's 'deal of the century' unfolding, as we explained previously.

Putin is capitalizing on the chaotic retreat of the US & Turkey's brutality toward the Kurds in order to assert Russia's leadership. He contrasts how Russia has stood beside its beleaguered ally, Syria, while the US has abandoned both its allies, the Kurds and the Turks. https://t.co/NjBYZzwKCG — Joshua Landis (@joshua_landis) October 13, 2019

But Russia is most definitely a lead player in the Damascus-YPG (and SDF) reunion that now appears to be unfolding.

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A huge development after earlier in the day Sunday Defense Secretary Mark Esper announced Trump has ordered a "deliberate withdrawal" of 1,000 US troops in northeast Syria amid the advancing Turkish incursion: sources close to the Syrian government have announced the Syrian Army will move in to assist Kurdish militias in Kobani and Manbij.

This after shocking statements over the weekend by the head of the US-backed Syrian Democratic Forces (SDF), Mazlum Abdi, who told CNN, "I've been holding myself for two days from going to the press and saying that America abandoned us and that I would like you to get out of our areas now so that I can invite Russian and [Syrian] regime planes to take over this airspace."

Syrian Army, via AFP/Getty

Reuters now reports on the significant development which could see the Turkish and Syrian armies enter into direct confrontation: "The Lebanese broadcaster al-Mayadeen said on Sunday the Syrian army would deploy within 48 hours to the town of Kobani which is held by the Kurdish-led Syrian Democratic Forces and the nearby town of Manbij which is controlled by SDF-aligned forces."

"The Syrian Governmental Forces (SAA) are preparing to enter the region of Kobani today, based on an agreement with the Syrian Democratic Forces," Syrian official Mohammed Shaheen, was cited as saying.

As early as last week the SDF was reportedly engaged in intensifying talks with Damascus over assistance from the Syrian Army, after the US withdrew its air support for the Kurdish-led group amid the Turkish assault.

On Monday the commander of the US trained and armed SDF, Mazlum Abdi, indicated just that in a bombshell statement: “We are considering a partnership with Syrian President Bashar al-Assad, with the aim of fighting Turkish forces.”

Though Damascus has yet to confirm an official deal with YPG/SDF forces, state-run SANA did say on Sunday that national forces were moving north to "confront" Turkish forces and its "aggression".

Military analysis site, The Defense Post, reports on the potential direct cooperation between the Syrian Army and SDF to push out the Turks:

Kobani official General Ismet Sheikh Hasan said that Russian and Syrian government troops could enter Kobani and Manbij by Sunday night to help secure the cities from a Turkish incursion. “We did everything we could,” he said. “We have called upon the West [and] the Arab Union but no one is coming to help, so we have no one other than ourselves to defend [Kobani]. Kurdish youth should come and defend their homes, and people should not abandon their homes – this is our land. It looks like this is the fate of the Kurds, to go through this each time.”

#BREAKING: Official statement of #Syria Arab Army: Soon, the #SAA will enter #Qamishli, #Manbij & other cities to prevent their fall into hands of #Turkish backed terrorists. They will also confront terrorists in Ras al-Ayn & Tal Abyad.#SAA defends the Kurds against #Erdogan pic.twitter.com/sPtQaJTLsa — Babak Taghvaee (@BabakTaghvaee) October 13, 2019

Damascus officials had subsequently denied that it was engaged in a wide-ranging deal, however, Sunday's reported development of Syrian Army forces to the north could be the beginning of a more significant deal in the words.

The United States has blocked such talks and cooperation for years, but the White House now appears ready to wash its hands of the matter.