The Syrian Observatory for Human Rights, a London-based war monitor, said that Russian air raids targeted positions in Idlib's southwest held by the hard-line Ahrar al-Sham group, as well as the Hayat Tahrir al-Sham Islamist alliance, which is led by a group affiliated with Al-Qaeda.
Syrian President Bashar al-Assad has massed his army and allied forces on the front lines in the northwest, and Russian planes have joined his bombardment of rebels there, in a prelude to a widely expected assault despite objections from Turkey. Dunford later added: "He expects us to have military options and we have provided updates to him on the development of those military options".
Yet, given Trump's willingness to place "maximum pressure" on Iran and his recent warning against the upcoming Syria offensive in Idlib, it seems likely that he would support the plan, especially as it is backed by his closest advisors, Bolton and Pompeo.
"We are living in black days", said one woman in Idlib.
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.
Smoke rising over buildings that were hit by airstrikes, in al-Sahan village, in the northern province of Idlib, Syria. The Russians and Iranians would be making a grave humanitarian mistake to take part in this potential human tragedy. "Don't let that happen!"
The US state department warned on Monday that Washington would respond to any new chemical attacks by the Syrian government or its allies.
Another "tool" in the United States arsenal is economic pressure.
The rebel-held enclave includes most of Idlib province and Hama province.
Even American airstrikes launched against the Assad government have had limited impact in the past. The Syrian government has been repeatedly accused of using chemical weapons in the long conflict. "As far as we can see, this is also the goal of the attempts to stage chemical weapons incidents by Syrian authorities".
Further heightening the risk of risky escalation, the US carried out a military exercise in southeastern Syria on Friday that, according to the military, included a "live-fire rehearsal" and an "aerial assault".
On Thursday, the new United States envoy for Syria, Jim Jeffrey, said the anticipated conflict would be a "reckless escalation", and that "there is lots of evidence that chemical weapons are being prepared".
Officials and analysts will be watching Idlib closely over the next week ahead of UN-led talks on Syria in Geneva on September 14. Renewed chaos in Idlib could potentially jeopardise such gains, and draw its proxies into the crosshairs of the Russian air force, which played decisive roles in the battles for east Aleppo and eastern Ghouta, both of which have been returned to regime control.
Heras warned that the Trump team is late to formulate a coherent Syria policy.