For Russia and Iran, both allies of the Syrian government, retaking Idlib is crucial to complete what they see as a military victory in Syria's civil war after Syrian troops recaptured almost all other major towns and cities, largely defeating the rebellion against Assad.
If this happens, its first stage will target northern Latakia province and the area around the town of Jisr al-Shaghour in southern Idlib, he said.
Almost 60 Russian air raids hit the south and southeast of Idlib province in less than three hours, the Syrian Observatory for Human Rights said. There is no word so far on casualties.
Idlib straddles major highways across Syria and if it is retaken by the government, the rebels would be left with just a few isolated pockets of territory. However, the Post article itself admits that 14,000 fighters in Idlib are linked to al-Qaeda, though the figure is likely much higher.
The vast majority of Idlib's population are civilians, who risk being massacred.
The United Nations and aid groups have warned a military campaign could spark one of the worst humanitarian catastrophes in a war that has already killed more than 350,000 people and displaced millions.
Around 3 million people live in the rebel stronghold in northwest Syria, which comprises most of Idlib province and adjacent small parts of Latakia, Hama and Aleppo provinces.
Erdogan, speaking at a summit in Tehran on Friday between Turkey, Iran and Russian Federation, urged the other leaders to support his call for an immediate cease-fire in the northwestern province of Idlib.
Turkey - which has long backed some rebel groups - fears a final assault will trigger another major refugee crisis on its southern border.
Erdogan, in his opening remarks, said a ceasefire in Idlib would be a victory for their summit.
The parties involved in the conflict of Idlib should practice "patience and use wisdom" to solve the issue in Idlib, Erdogan said in an address to a summit in the capital Tehran attended by Russian President Vladimir Putin and Iranian President Hassan Rouhani.
Thousands of people took to the streets in Syria's Idlib Province to protest against an assault promised by President Bashar al-Assad's forces that the United Nations has warned could cause a humanitarian disaster. "We never want to see Idlib turn into a lake of blood".
He did not give details of the evidence he was referring to.
"But we are in a dialogue, a routine dialogue, with the president to make sure he knows where we are with regard to planning in the event that chemical weapons are used", Dunford told reporters during a trip to India.
"The legitimate Syrian government has a right and must eventually take under control of its entire national territory", Putin declared.