The United States said Thursday it had confirmed the Syrian government used chemical weapons against rebels last year and said it would provide more aid, including "military support," for forces opposing President Bashar al-Assad.
Up to 150 people are estimated to have died in Syria as a result of chemical weapon attacks by the Assad regime against opposition forces, it said. The Syrian government has denied any use of chemical weapons and rejected U.N.-led fact-finding.
"Our intelligence community assesses that the Assad regime has used chemical weapons, including the nerve agent sarin, on a small scale against the opposition multiple times in the last year," Ben Rhodes, deputy national security adviser, told reporters.
President Barack Obama has made it clear that the use of chemical weapons or transfer of them to terrorist groups is "a red line," given the long-established international norm against their use, Rhodes also said.
The announcement came ahead of next week's summit in Northern Ireland of the Group of Eight major nations, including the United States and Russia, which is supportive of the Assad regime.
Rhodes said Obama decided to provide more backing, including military support. But he remained vague about whether the support referred to provision of weapons, from which the U.S. government has refrained so far.
Washington currently provides Syrian rebels with non-lethal military supplies.
The French government said earlier this month that it has obtained evidence that shows the Assad regime has used sarin in confrontations in Syria.
In April, Washington said the U.S. intelligence community cited the possibility that the Syrian government used sarin against rebels.
The Syrian government has denied it used chemical weapons and rejected a call by U.N Secretary General Ban Ki Moon to allow a fact-finding mission in the country.