The US has said it will provide military assistance to Syrian rebel groups.
President Barack Obama made the decision after his government came to the conclusion that chemical weapons had been used by President Bashar al Assad’s forces.
Ben Rhodes, a deputy national security adviser, would not go into detail about the weaponry the US intends to supply.
He said: “The President has made a decision about providing more support to the opposition. That will involve providing direct support to the SMC (the Supreme Military Council). That includes military support.
"I cannot detail for you for a variety of reasons, but suffice it to say this is going to be different in both scope and scale in terms of what we are providing to the SMC than what we have provided before.”
Russia said that it was not convinced by the US claims about the use of chemical weapons.
British Foreign Secretary William Hague agreed with the US assessment and said that he would "urgently" discuss the UK response.
Mr Hague said Britain and other countries must "be prepared to do more to save lives" in Syria.