Turkey’s President Recep Tayyip Erdogan on Wednesday threatened to launch an operation in Syria’s Idlib region by the end of the month if Damascus fails to withdraw behind Turkish military positions.

“An operation in Idlib is imminent,” Erdogan told his party’s lawmakers in parliament. “We are counting down, we are making our final warnings”.

Russia – the Syrian government’s main ally in the nine-year war – responded by saying any Turkish offensive against Syrian forces in Idlib would be a “worst case scenario”.

Erdogan said talks with Russia on the northwestern Syrian region were far from meeting Turkey’s demands, and warned a military operation was just a “matter of time”.

Speaking to lawmakers from his ruling AK Party, Erdogan said Turkey was determined to make Idlib a secure zone “no matter the cost”, even as talks continue with Russia, which backs Syrian President Bashar al-Assad’s forces.

The comments came as Syrian troops pressed an offensive on the country’s last major rebel enclave.

About 900,000 people have been forced from their homes and shelters in less than three months.

Erdogan’s announcement comes a day after dire warnings by United Nations officials who warned of a humanitarian disaster in northwest Syria. 

Nearly 300 civilians have been killed in attacks this year in the region, with 93 percent of the deaths caused by Syrian and Russian forces, according to the UN’s human rights chief.

President al-Assad pledged this week to continue the onslaught on the country’s last major rebel stronghold, saying the war was not yet over but a “complete victory” was in sight.