U.S. Secretary of State John Kerry says it is "undeniable" that chemical weapons recently were used in Syria, and he calls the action a "moral obscenity."
Speaking at the State Department Monday, Kerry said President Barack Obama believes there must be accountably for those who would use what he called such "heinous weapons." He did not say what actions the president might take.
A White House spokesman Monday said President Obama is evaluating the appropriate response, but has made no decision on how to respond. He said there is "very little doubt" that the Syrian government was behind the use of the chemical weapons.
Kerry said that in the days following the reports of the chemical weapons attack, the Syrian government refused access to the site, and instead shelled the area. He said "that is not the behavior of a government that has nothing to hide."
There has been mounting pressure on the United States and other countries to address Syria's two-year conflict, following allegations last week that chemical weapons were used outside of Damascus, killing hundreds of people.
President Obama said last year that chemical weapons use in Syria would cross a "red line,'' and likely would change his calculation in deciding on a U.S. response. However, the president took little action after reports earlier this year that chemical weapons were used on a small scale in Syria.
Earlier Monday, U.S. Defense Secretary Chuck Hagel said any action on Syria will be taken "in concert with the international community and within the framework of legal justification." He made the comment on a visit to Indonesia.
Some U.S. lawmakers, including Mr. Obama's opponent in the 2008 presidential election, Senator John McCain, have called for limited strikes against Syrian military targets.