Turkish and Russian officials held three hours of seemingly inconclusive talks over Syria's Idlib, but they agreed to meet again next week.
"The situation in Idlib was discussed," Turkey's foreign ministry said after the talks. "Steps that could be taken to establish peace on the ground as soon as possible and advance the political process were evaluated."
Turkey had threatened on Saturday to respond if any of its military outposts in Syria's last opposition bastion of Idlib came under attack, a day after officials said three of them had been encircled by forces loyal to Damascus.
The warning came as a Russian delegation was due to arrive in Ankara for talks over the situation in the rebel-held province.
Under an agreement with Russia, key ally of President Bashar Al Assad's regime, Turkey has set up 12 observation posts in Idlib to avert an offensive by Syrian government forces.
Regime forces backed by Russian air strike have made significant gains in Idlib over recent weeks. On Saturday they completed the takeover of Saraqeb, a town that sits on the intersection of two major highways that the government wants to control.
Earlier this week Turkey sent nearly 150 vehicles with commandos and ammunition to beef up its observation positions, with officials on Friday reporting that three of them had been surrounded by regime troops.
"Our observation posts in Idlib continue their duties and are capable of protecting themselves with the weapons and equipment they possess," the Turkish defence ministry said on Twitter.
"In the event of a new attack, proper response will be given in the strongest manner, based on the right of self-defence."
The Syrian Observatory for Human Rights, a UK-based war monitor, said on Saturday that 430 Turkish military vehicles had crossed into Idlib in the last 24 hours. All the Turkish reinforcements were deployed to outposts behind the front line north of Saraqeb town, it said.
"They have formed a buffer blocking further regime advances in Idlib," Observatory head Rami Abdel Rahman said.
Some Turkish troops were seen heading towards a military airport in the Taftanaz area, 16 kilometres north of Saraqeb. Others were deploying to a military base south of Idlib city.
President Recep Tayyip Erdogan gave Syria an ultimatum to withdraw its troops from its military observation posts by the end of February after eight Turks were killed in regime fire on Monday.
The deadly clashes have angered Turkey, which urged Moscow to press the regime for an end to its offensive.
Turkey and Russia have worked closely in recent years to resolve the situation in Idlib despite being on opposing sides of the conflict.
The regime forces have pressed their offensive despite Tureky's warnings and are close to seizing complete control of two key highways that are believed to be the main objective of their campaign.
"Regime forces have seized the entire section of the Damascus-Aleppo highway that runs through Idlib province," Mr Abdel Rahman said.
State media made no mention of control over that part of the M5 motorway, but said that government forces had taken control of two villages along the road.
The M5 has long been in the sights of the Damascus regime, as retaking it would allow traffic to flow from the capital to second city and former industrial hub Aleppo.
The Observatory said the latest advance to the north-east of Saraqeb and gains the area of Al Eis in the south of Aleppo province meant government fighters only had a 15 kilometre stretch remaining to seize in Aleppo province to exert full control over the highway.
Running up from the Jordanian border in the south of the country, the M5 is Syria's longest highway. It cuts through fertile fields, industrial zones and four major cities.
The violence in Idlib since December has forced more than 580,000 people out of their homes, in one of the biggest upheavals in the nine-year civil war.
Just a few months ago, Saraqeb counted some 110,000 residents, according to the Observatory. But weeks of deadly bombardment by the government and Russia levelled much of the town and sent its inhabitants fleeing northwards towards the Turkish border.
More than 300 civilians have been killed in Idlib region in recent months, according to the Observatory.
Syria's war has killed more than 380,000 people and displaced more than half the country's pre-war population since starting in 2011 with the brutal repression of anti-government protests.
