"I am very sure that we have very, very good grounds to be making these warnings", said Jim Jeffrey, who was named on August 17 as Secretary of State Mike Pompeo's special adviser on Syria overseeing talks on a political transition in that country. "Any offensive is to us as objectionable as a reckless escalation".
The UN Security Council is also due to meet Friday to address the situation in Idlib amid growing fears of an attack and the possible use of chemical weapons.
Trump and his top officials have called attention to the impending Syrian government offensive in recent days, warning the Syrian regime and its backers Russian Federation and Iran not to use chemical weapons or recklessly cause civilian deaths.
The Russian Defense Ministry has published footage showing how its military jets use high precision weapons to knock out what it claims are the locations of Jabhat an-Nusra terrorists in Syria's Idlib province.
Part of the motivation for this change is uncertainty about whether Russian Federation is willing or able to help get Iran - which along with Russian Federation is Syrian President Bashar al-Assad's closest ally - out of the country.
Russian Federation says it has launched airstrikes targeting militant infrastructure in Syria's northern Idlib province, where the government is expected to launch a major offensive against the rebels' last major stronghold.
"The fact is that there are no representatives of the armed opposition here around this table".
A United Nations team takes samples from the scene of a suspected chemical weapon attack, in the Damascus countryside in August 2013.
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The Centers for Disease Control is assisting state health officials in confirming the source of the outbreak. The disease can not be spread through person-to-person contact, nor by drinking contaminated water.
HTS controls more than half of Idlib province, while other rebels, including Ahrar al-Sham, hold most of the rest.
The three nations past year declared Idlib to be a "de-escalation zone", and Turkey says the cease-fire inside Idlib must not be violated. The Turks are trying to find a way out.
"Whatever reason there is an attack that has been made or will be made will result in disaster, massacre and humanitarian drama", he said.
Rouhani also said that the intervention of the United States should end, and that any interference without the cooperation with Assad government will "cause this crisis to become deeper". There was a "a new commitment" by the administration to remain in Syria until Islamic State militants were defeated, while ensuring Iran left the country, he added.
Trump will chair a UN Security Council meeting on Iran during an annual gathering of world leaders in NY later this month.
Tehran and Moscow have helped Assad turn the course of the war against an array of opponents ranging from Western-backed rebels to Islamist militants, while Turkey is a leading opposition supporter and has troops in the country. He said Assad has "no future as a ruler" of Syria but that it was not Washington's job to get rid of him.
One of the newly sanctioned individuals, Muhammad al-Qatirji and his company Qatirji Company, maintain "strong ties to the Syrian regime and facilitates fuel trade between the regime and ISIS, including providing oil products to ISIS-controlled territory", according to information provided by the Treasury Department, which oversees and enforces sanctions.