Turkey said on Friday Syrian government forces were violating a ceasefire agreement reached with Russia for Syria's Idlib.
Russia has backed the government of Syrian President Bashar al-Assad, while Turkey has backed some rebels in Syria's eight-year-old civil war, but they have worked together to try to contain fighting in the country's northwest.
In recent weeks, that effort has been strained by the surge in violence in Idlib, the last major insurgent stronghold.
"The regime is not keeping its promises of a ceasefire despite the agreement and is violating the ceasefire," Defense Minister Hulusi Akar said in a statement on the ministry's website, adding that an escalation in violence could lead to a humanitarian tragedy.
"The Sochi agreement requires a ceasefire and that is what we want from the Russians. Meetings in Ankara are continuing right now," he said.
The ministry earlier said a joint working group between Ankara and Moscow had met in the Turkish capital on Thursday and Friday to discuss Idlib, the Sochi agreement and the Astana process - multi-sided efforts to try to provide stability in Syria.
Moscow had been piling pressure on Ankara to start an operation against the opposition-held areas after Turkey's failure to push rebels to agree to Russian patrols and get al Qaeda-inspired militants out of a buffer zone that underpinned the Turkish-Russian deal.