The government of Syrian President Bashar al-Assad appears to be quietly shifting some chemical weapons from storage sites, Western and Israeli officials have said, but it is not clear whether the operation is merely a security precaution amid Syria's escalating internal conflict, or something more.
"There are certain responsibilities that go along with the handling and storage and security of those chemical weapons," White House spokesman Josh Earnest told reporters when asked whether there was any US intelligence that backed up news reports on the prospects for Syria resorting to chemical weapons against its opponents.
"We believe that the individuals who are responsible for living up to those challenges should do so and will be held accountable for doing so," he said aboard Air Force One as President Barack Obama headed for Texas.
Mr Earnest said he could not discuss specific intelligence on Syria's chemical weapons. But he said President Obama and other world leaders were concerned overall about "inhumane brutality" by the Syrian government against its own people.
Some analysts say Mr Assad's government may be shifting some of its stockpile to keep the weapons from capture by an expanding insurgency, and to deprive Syria's Western foes of an excuse for intervention on the grounds of securing dangerous material gone astray.
The Syrian government denies carrying out the operation. Syria's undeclared stockpile -- believed to be the largest of its kind in the Middle East -- reportedly includes sarin nerve agent, mustard gas and cyanide.