National security adviser H.R. McMaster on Saturday called on the international community to hold Syrian President Bashar Assad accountable for his use of chemical weapons, Reuters reported.

"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 at a conference in Munich.

McMaster said public accounts and photos show evidence Assad is continuing to use chemical weapons. He was echoing claims from other U.S. and foreign officials.

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As the Syrian conflict rages on, Assad's government has faced allegations in recent weeks of repeatedly using chlorine bombs in rebel-held areas of the country. The Syrian government has denied such claims.

Secretary of State Rex Tillerson Rex Wayne TillersonGary Cohn: 'I haven't made up my mind' on vote for president in November Kushner says 'Alice in Wonderland' describes Trump presidency: Woodward book Conspicuous by their absence from the Republican Convention MORE told CBS's “60 Minutes” that a U.S. military response to the use of chemical weapons remains an option.

"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 said.

Tillerson’s comments echo those of French President Emmanuel Macron, who said last week his country “will strike” if Assad’s government uses chemical weapons on civilians.