White House national security adviser H.R. McMaster, speaking at the Munich Security Conference in Germany Saturday, called on "all nations" to hold the Syrian regime and related entities accountable for their actions, citing chemical weapons attacks on the Syrian people.

"Public accounts and photos clearly show that Assad's chemical weapons use is continuing," McMaster told the attendees. "It is time for all nations to hold the Syrian regime and its sponsors accountable for their actions, and support the efforts of the Organization for the Prohibition of Chemical Weapons."

McMaster said did not specify which reports or accounts "clearly show" that Syrian president Bashar al-Assad is using chemical weapons upon his people. But the U.S. suspects the Syrian regime is connected to multiple chlorine gas attacks in Syria in the last month alone.

Secretary of State Rex Tillerson had a similar message in an interview with CBS News White House and senior foreign affairs correspondent Margaret Brennan that will air in full on "60 Minutes" on Sunday. Tillerson said military action is still on the table as a response for any use of chlorine gas.

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"As it was in April last year, we are serious about our demands that chemical weapons not become regularized or normalized as a weapon in any conflict," Tillerson told Brennan.

Last April, a chemical weapons attack in Syria — that the Trump administration blamed on Assad — killed dozens of Syrians. President Trump responded by striking a Syrian air base to destroy some of the regime's equipment.

Tillerson said Russia needs to step up and take responsibility for Syria, given that it committed to helping destroy Syria's stockpile of chemical weapons.

"Russia has special responsibilities, in our view, because of commitments they made ... to destroy chemical weapons and ensure …they knew there were none," Tillerson said.