Barack Obama has emphasised US concerns about Syrian chemical weapons in a phone conversation with Russian President Vladimir Putin today, the White House said.
"President Obama and President Putin reviewed the situation in Syria, with President Obama underscoring concern over Syrian chemical weapons," a White House statement said.
The two leaders agreed to stay in touch on the issue and that Secretary of State John Kerry and Russian Foreign Minister Sergei Lavrov would continue discussions on Syria.
ITV News has spoken to people inside Syria who claim they have suffered the effects of chemical weapon attacks by President Assad's forces.
President Obama and David Cameron reacted today to reports of the Syrian government using chemical weapons on civilians.
Britain and the United States have declared they have found evidence that chemical weapons have been used in Syria's bloody civil war.