Turkish Foreign Minister Mevlut Cavusoglu warned Russia on Friday that seeking a military solution in Syria's last rebel-held province of Idlib would be disastrous.
"A military solution there will cause catastrophe," Cavusoglu said at a press conference in Moscow with Russian counterpart Sergei Lavrov, before meeting Russian President Vladimir Putin.
"Not only for the Idlib region but for the future of Syria, it will cause catastrophe and the clashes may last a long time," he warned.
Speculation is increasing that there could be a Russian-backed government assault on the northwestern province, home to Syria's last major rebel stronghold.
Syrian President Bashar al-Assad's regime still holds Idlib's southeastern tip and he has set his sights on retaking control of the region, which borders Turkey, calling this one of his priorities.
Cavusoglu warned of the risk heavy fighting would pose to the large civilian population.
"Civilians will be harmed. Where will the 3.5 million civilians go?" he asked, as Turkey has already taken in more than three million refugees from Syria.
- 'Halt refugee influx -
Idlib is one of the so-called "de-escalation" zones set up as a result of talks by Russia, Turkey and Iran last year.
Cavusoglu stressed the need to keep the de-escalation zone in place "to halt any refugee influx".
"It's also important for Turkey because they are on the other side of our border. They pose a threat to us first," he added.
Nonetheless rebel-backer Turkey considers "it is very important that those radical groups, terrorists are rendered ineffective," he said.
Putin later met both the Turkish foreign and defence ministers in Moscow.
In televised comments the Russian leader said that through the efforts of Russia, Turkey and other countries, they had "managed to seriously move forward in settling the Syrian crisis".
Yet the situation in Syria remains one of the "burning questions" for Russia, he admitted.
Russia's Lavrov on Friday called the situation in Idlib "multi-faceted" and called for separating out "the healthy opposition from terrorist structures".
"When the de-escalation zone was created in Idlib, no one proposed using it for terrorists to hide behind the civilian population like a human shield," he said.
"Especially as they aren't just lying low there. Raids are constantly coming from there as well as firing on the positions of the Syrian army".
- Strategic role -
The Turkish foreign minister said Ankara would still rely on talks with Russia and Iran, known as the Astana peace process, widely seen as an attempt to circumvent largely fruitless UN talks on Syria.
The high-level visit to Russia by Turkish ministers comes as Turkey is feuding with NATO ally United States over an American pastor held for two years on terror charges.
US President Donald Trump this month announced sanctions against Turkey that caused the lira to plunge in value.
Idlib is a strategically important province adjacent to Latakia, a regime stronghold on the Mediterranean coast that is home to Assad's clan.
The jihadist Hayat Tahrir al-Sham (HTS) alliance controls around 60 percent of Idlib while other Turkey-supported rebel groups hold most of the rest.
Analysts say any regime offensive will probably be limited to a small area of Idlib, with a deal between Russia and Turkey likely to determine the fate of the rest of the province.
More than 350,000 people have been killed and millions displaced since Syria's war started in 2011 with the brutal repression of anti-government protests.
Russia began a bombing campaign in support of Assad's regime in September 2015 and has helped him win back large parts of the country.