Russia's Defense Ministry has said that a fake chemical attack on civilians has been filmed in the northwestern Syrian province of Idlib.
"It is absolutely essential to avoid a full-scale battle in Idlib", Guterres told reporters at United Nations headquarters.
The resulting impact on civilians has been dramatic, Laerke said, his concerns echoing those of UN Emergency Relief Coordinator Mark Lowcock, who a day earlier had issued a warning about a military escalation in Idlib, after a recent meeting with Syria government officials in the country's capital.
"A regime assault would also create serious humanitarian and security risks for Turkey, the rest of Europe and beyond", he would add.
The latest escalation comes as residents of Idlib and many players in the worldwide community, including President Trump and Vice President Mike Pence, express new concerns about a Syrian attack on Idlib.
Turkey, Russia and Iran a year ago set up the Astana process, a negotiating track to end Syria's war that complements the UN-led peace process.
The UN warned Monday at least 30,000 residents in Idlib have been displaced in the first nine days this month amid the Russian and regime air campaign there.
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The week-long war games "have kicked off" in far eastern Russia, AFP quoted Russia's defence ministry as saying. Defence Secretary Jim Mattis said he did not see the two countries aligned in the long-term".
In Idlib, civilians and fighters have been scrambling to prepare for the looming offensive.
Last week's summit in Tehran between the three sides did not produce any agreement, as Iran and Russian Federation rejected Turkey's call for a continued ceasefire in the rebel bastion.
United States officials have in recent days said additional action would follow if Assad were to use the banned weapons in rebel-held Idlib.
"I think ideally we'd like to stop the regime assault and win some time to move HTS out of idlib", said one Turkish official, speaking anonymously to discuss a sensitive matter.
"All we've seen are the actions of cowards interested in a bloody military conquest of Idlib".
It is unclear when the offensive will formally begin and what impact the fall of Idlib could have on Turkish-controlled Afrin and the northern provinces controlled by the US-backed and Kurdish-led Syrian Democratic Forces (SDF).
While officials in Washington, along with counterparts from European allies, are preemptively positioning to use chemical weapons attacks as a pretense for possible airstrikes, Russian Federation has pointed the finger at the USA for breaking global law with the use of white phosphorus bombs. "The world will hold them responsible", she added. Since then, hundreds of thousands of people have been killed in the conflict and millions more displaced, according to the UN.