The United States warned on Sunday the Syrian regime against carrying out a weaponized gas attack in the country amid unconfirmed reports of chlorine attacks in Eastern Ghouta. “It would be very unwise for them to use weaponized gas. And I think President Donald Trump made that very clear early in his administration,” US Defense Secretary Jim Mattis said, speaking with a small group of reporters before landing in Oman. He said that he was disturbed by reports of civilian casualties from bombings by regime head Bashar Assads forces. "Right now were getting reports — I dont have evidence that I can show you — but Im aware of the reports of chlorine gas use," he stated. Mattis stopped short of threatening to retaliate against the regime if a chlorine attack were confirmed. But he noted America’s cruise missile strike on April 6, 2017, on a Syrian air base over a sarin gas attack and said President Donald Trump had “full political maneuver room” to take whatever decision he believed was appropriate. Rescue workers and opposition activists in Eastern Ghouta have accused the regime of using chlorine gas during the ongoing campaign there. The Syrian regime has vowed to continue the offensive in Eastern Ghouta, one of the deadliest in the war. In Washington, CIA director Mike Pompeo noted that Trump has said he will not tolerate chemical weapons attacks, but has not yet made a decision about the latest reports. "In this case, the intelligence community is working diligently to verify what happened there," Pompeo said in an interview on CBS "Face the Nation." "Ive seen the pictures. Youve seen the pictures as well. We have a higher standard to make sure we understand precisely what took place, precisely who did it so that our response can meet the threat." Mattis, meanwhile, chided Moscow for partnering with Assad, suggesting it might even be a partner in the regime’s strikes on civilians. “Either Russia is incompetent or in cahoots with Assad. There’s an awful lot of reports about chlorine gas use or about symptoms that could be resulting from chlorine gas,” Mattis said. The United Nations High Commissioner for Human Rights said earlier this month that regime air strikes on Eastern Ghouta probably constitute war crimes. The White House said last week Russian military aircraft took off from Humaymim Airfield in Syria and carried out at least 20 daily bombing missions in Damascus and Eastern Ghouta between February 24 and 28. It did not say whether the jets dropped ordnance, which could be harder to determine than tracking the flight paths of Russian aircraft on US radar. But the United States directly accused Russia of killing civilians. Mattis declined to elaborate on whether Russian jets directly carried out bombings, saying Moscow was involved either way. “They are Assad’s partner and whether the airplane dropping the bomb is a Russian airplane or a Syrian airplane, I’d prefer not to say right now,” he said. The Britain-based Syrian Observatory for Human Rights monitoring group says an indiscriminate campaign of regime and Russian air strikes and shelling has killed some 1,100 civilians in rebel-held Eastern Ghouta over the past three weeks. The UN estimates 400,000 civilians are trapped in the siege.