President Barack Obama has asked the US Congress to approve $500m (£294m) to train and equip what he described as “moderate” Syrian opposition forces.
The funds would help Syrians defend against forces aligned with President Bashar al-Assad, the White House said.
The aid would also counter Islamist militants such as the Islamic State in Iraq and the Levant (Isis), it added.
Isis’s advance in neighbouring Iraq has led some in Congress to press Mr Obama to take action.
Tens of thousands of people have died and millions more have been displaced in three years of civil war in Syria, as rebels fight troops loyal to Mr Assad. . .