Talking to the Atlantic monthly, Clinton used harsh words to describe the failure that resulted from Obama's decision to stay on the sidelines during the first phase of the Syrian conflict, where the opposition has been trying to topple President Bashar al- Assad, xinhua reported.
"The failure to help build up a credible fighting force of the people who were the originators of the protests against Assad -- there were Islamists, there were secularists, there was everything in the middle -- the failure to do that left a big vacuum, which the jihadists have now filled," she said.
Serving as the top American envoy during Obama's first term, Clinton is widely expected to make another run for the presidency and is seen as trying to distance herself from the president, whose foreign policy has been under sharp attack in recent months.
The US fighters and drones have launched air raids on targets of the Islamic State of Iraq and Syria (ISIS) in northern Iraq for three consecutive days since Obama authorised the move Thursday to protect Americans as well as to conduct humanitarian missions.
Echoing some Republicans, Clinton said Obama lacked a strategy for confronting the threats posed by Islamic militants.
"Great nations need organising principles, and 'don't do stupid stuff' is not an organizing principle," she said, referring to a slogan coined by the president recently to describe his foreign-policy doctrine.