(CN) — A day after U.S. officials called it “highly likely” that Syrian President Bashar Assad kept a hidden stockpile of chemical weapons, Defense Secretary Jim Mattis told reporters Friday that there is no evidence Syria used sarin on its citizens.
Speaking at the Pentagon this morning, Mattis said the U.S. is looking for evidence to support claims to the contrary being pushed by aid groups and others in Syria.
Assad has denied that his government used illegal chemicals, but Mattis called it undeniable that Syria has weaponized and used chlorine gas in its civil war.
Chlorine has nonchemical uses that make it easier to acquire. Mattis said the possible use of the nerve agent sarin has the U.S. "even more concerned. Sarin is a colorless and tasteless toxin that can cause respiratory failure leading to death.
Reports of chemical attacks streamed in from Syria as recently as Thursday, the Associated Press reported.
In the rebel-held Damascus suburb of Douma, rescue workers reportedly described a suspected chlorine gas attack that injured a number of civilians. The opposition-run Ghouta Media Center disclosed on Facebook page meanwhile that surface-to-surface missiles, some of them carrying chlorine gas, killed three people and caused shortness of breath in dozens others.
“The reports could not be independently verified and the Britain-based Syrian Observatory for Human Rights, which monitors the war in Syria via activists on the ground, was unable to confirm the reports either,” according to the AP report. “The accounts followed a suspected attack in late January near Damascus that activists and rescue teams said affected nearly 20 civilians.”
Speaking to the Associated Press on condition of anonymity Thursday, officials with the Trump administration accused Assad's government of violating the terms of a 2013 commitment to abolish its weapons program.
Rather than developing new, deadlier chemicals, Assad's forces are likely using the same chemicals — chlorine and sarin — but in more sophisticated ways that makes their origins harder to trace, the officials said.
They noted that ground-launched munitions, for example, have taken the place of barrel bombs used earlier in the war to disperse chemicals indiscriminately.
Calling it "highly likely" that Assad kept a hidden stockpile of chemical weapons that he failed to properly disclose, U.S. officials said its investigation of recent alleged attacks suggests that Assad also retained a "continued production capacity" — which the 2013 deal also banned.
The officials emphasized that the United States is looking to Russia, Assad's patron, for cooperation in pressuring Assad to end chemical-weapon attacks.
Russia has characterized the reports about Syria’s chemical attacks as attempts by opposition groups to pressure the government or cause disruption.
The United States brokered the deal to rid Syria of its stockpiles with Russia under President Barack Obama. Another alleged attack in April 2017 led President Donald Trump to ordered a retaliatory missile strike, but the U.S. and international observers say the weapons are still used 10 months later.
The Joint Investigative Mission, an expert body set up by the United Nations and Organization for the Prohibition of Chemical Weapons, determined that Assad's government used chlorine gas in 2014 and 2015, and sarin in April 2017. Both the Russian and Syrian governments have rejected these conclusions.
Calling the investigative body discredited, Russia used its veto power on the U.N. Security Council to prevent the mission’s renewal late last year. The U.S. and other nations responded by accusing Moscow of covering for Assad's forces.
As reported by the AP, the Trump officials said the United States relies on third countries to conduct sample testing on evidence that is otherwise difficult to collect from a war zone, and that it also relies on intelligence and open-source information from social media and other outlets.
Though experts have questioned why Assad would carry out attacks that inspire so much criticism, the officials said “the U.S. believes Assad's government sees chemical attacks as an effective way to terrorize rebels and sympathetic populations into fleeing, therefore altering the demographic balance in the Alawite heartland where Assad is trying to consolidate control,” according to the AP’s report.
The Alawite sect is an offshoot of Shiite Islam that forms a minority of Syria's population, and Assad is a member.
Chemical weapons have been used by the Islamic State group as well, the officials agreed, but they said these attacks have been more rudimentary.
The extremist group is said to use easily obtainable chemicals like sulfur mustard and chlorine, dispensing them via artillery shells and improvised explosive devices.
Associated Press writers ROBERT BURNS, ZEINA KARAM and JOSH LEDERMAN contributed to this report.