Turkish President Recep Tayyip Erdogan said on Wednesday that Turkey has started providing complete support to rebel groups against the advancing pro-Syrian government forces, and threatened to shoot down aircraft targeting civilians in embattled Idlib province.

Meanwhile, US troops and pro-government forces confronted one another at a checkpoint near the eastern city of Qamishli, with the Americans conducting a warning air strike and retreating.

“Regime and Russian forces, along with Iran-backed militants, continuously attack civilians and conduct massacres and shed blood,” Erdogan said at a ruling AK Party parliamentary group meeting.

Erdogan said Turkey is adamant that by the end of the month it will push back President Bashar al-Assad's forces to the de-escalation line previously ringing Idlib.

“We will use whatever tools necessary on the ground and air, without any hesitation,” he added.

'We will use whatever tools necessary on the ground and air, without any hesitation' - Recep Tayyip Erdogan

Rebel-backer Turkey has found itself squeezed in Idlib, a northwestern province that has become the Syrian opposition's last redoubt. Some three million people live in rebel-held territory there, but a pro-government offensive has since December has displaced around 700,000 people towards the Turkish border.

Ankara already had several military observation points in Idlib, as part of a de-escalation deal agreed with Assad ally Russia in Sochi in 2018, and six of its posts have been encircled by government forces since September.

However recent events have prompted Turkey to flood more troops, vehicles and equipment into Idlib, and double down its support for rebels, who have lost 600 square km in a matter of weeks. Syrian government and Russian aircraft have rained bombs down on Idlib, with some 350 civilians killed so far.

On Tuesday, a Syrian government helicopter, a Russian-made Mi17, was shot down by the rebels near the town of Neirab. Several sources on the ground interviewed by Middle East Eye said that the air defence system that hit that aircraft was provided by Turkey.

“Aircraft that target civilian residential areas won’t be able to move freely any longer. We will chase regime forces on the ground out of the borders we designated,” Erdogan said.

In an apparent rebuke to the Russians, the president also said Ankara would no longer wait for the results of endless meetings.

Russian state news agency Ria Novosti reported that Erdogan made a phone call to Russian President Vladimir Putin early on Wednesday before his fiery speech and discussed the Idlib crisis. “The importance of the full implementation of the existing Russian-Turkish agreements ... was noted," the Russian presidency said in a statement.

Several meetings conducted with Russians in Ankara since the weekend have collapsed. Turkish officials repeatedly told their counterparts that Syrian government forces must withdraw from the areas recently captured, including the highly strategic M5 highway. Turkish officials are expected to continue talks in Moscow.

“We fortified our military presence in Idlib in the last few days. We provide every sort of support to our Syrian brothers who started to move to push the regime out of the Sochi line,” Erdogan said.

A Syrian source, who spoke on condition of anonymity, told MEE that Turkey had transferred a large amount of advanced anti-tank weaponry along with grad missiles to the rebels in recent days.

“It is likely that the weaponry came from the US,” the source said.

A Turkish official declined to comment. The CIA provided similar aid to rebel groups fighting Assad between 2012-17.

The return of the legendary ATGM operator nicknamed 'Abu Tow' to the frontlines of #Idlib. This has much symbolic meaning. pic.twitter.com/nIbPA7bu1o — Ömer Özkizilcik (@OmerOzkizilcik) February 11, 2020

On Tuesday, US Secretary of State Mike Pompeo declared Washington's support for NATO ally Turkey, with tensions between Americans and Damascus loyalists breaking out in eastern Syria the next day.

A US military convoy was attacked at a checkpoint near the city of Qamishli with live fire, the United States-led coalition in Syria said in a statement, prompting the Americans to respond with gunfire and a warning air strike, before pulling back.

"After coalition troops issued a series of warnings and de-escalation attempts, the patrol came under small arms fire from unknown individuals," it said.

As for Idlib, Erdogan also said that, from now on, if further attacks against the Turkish observation posts occur, Turkey would retaliate against the government forces anywhere in Syria, regardless of the boundaries drawn up by the Sochi deal.

The announcement made by the Turkish president signals an unprecedented escalation between Turkey and the Damascus government.

Turkey's response has come in the wake of two separate Syrian government attacks targeting Turkish soldiers in Idlib over the past week, that left 13 of them dead.

Turkey-backed Syrian rebels began an offensive earlier this week to retake the strategic town Saraqeb that sits on M4 and M5 highways. Rebels briefly captured Neirab to the west of Saraqeb, but later retreated, according to aid workers on the ground interviewed by MEE.