President Trump Donald John TrumpOmar fires back at Trump over rally remarks: 'This is my country' Pelosi: Trump hurrying to fill SCOTUS seat so he can repeal ObamaCare Trump mocks Biden appearance, mask use ahead of first debate MORE on Monday warned Syrian President Bashar Assad and his allies Iran and Russia against attacking Syria’s rebel-held Idlib province, saying it would be a “grave humanitarian mistake.”

“President Bashar al-Assad of Syria must not recklessly attack Idlib Province,” Trump tweeted. “The Russians and Iranians would be making a grave humanitarian mistake to take part in this potential human tragedy. Hundreds of thousands of people could be killed. Don’t let that happen!”

President Bashar al-Assad of Syria must not recklessly attack Idlib Province. The Russians and Iranians would be making a grave humanitarian mistake to take part in this potential human tragedy. Hundreds of thousands of people could be killed. Don’t let that happen! — Donald J. Trump (@realDonaldTrump) September 3, 2018

U.S. Ambassador to the United Nations Nikki Haley Nimrata (Nikki) Haley'The soul' versus 'law and order' Author Ryan Girdusky: RNC worked best when highlighting 'regular people' as opposed to 'standard Republicans' GOP lobbyists pleasantly surprised by Republican convention MORE also warned against an attack, writing in a tweet: “All eyes on the actions of Assad, Russia, and Iran in Idlib. #NoChemicalWeapons”

All eyes on the actions of Assad, Russia, and Iran in Idlib. #NoChemicalWeapons https://t.co/DscJOxf4x1 — Nikki Haley (@nikkihaley) September 3, 2018

France also said there could be "disastrous consequences" if Syrian forces and their allies launch an assault on the Idlib province in northwestern Syria, the last major enclave held by rebels fighting the Iran and Russia-backed Assad regime.

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Secretary of Mike Pompeo Michael (Mike) Richard PompeoOvernight Defense: Pentagon redirects pandemic funding to defense contractors | US planning for full Afghanistan withdrawal by May | Anti-Trump GOP group puts ads in military papers Overnight Defense: House Democrats unveil stopgap spending measure to GOP opposition | Bill includes .6B for new subs | Trump issues Iran sanctions after world shrugs at US action at UN Navalny calls on Russia to return clothes he was wearing when he fell ill MORE on Friday tweeted that Russian Foreign Minister Sergey Lavrov “is defending Syrian and Russian assault” on the province and in another tweet wrote that the people of Syria “will suffer from this aggression.”

“Sergey Lavrov is defending Syrian and Russian assault on #Idlib. The Russians and Assad agreed not to permit this. The U.S sees this as an escalation of an already dangerous conflict,” Pompeo wrote.

“The 3 million Syrians, who have already been forced out of their homes and are now in #Idlib, will suffer from this aggression,” he continued. “Not good. The world is watching.”

According to a CNN report late last week, the U.S. has put together an initial list of Syrian chemical weapons facilities that could be targeted with airstrikes if Syria were to launch a new chemical weapon attack.