In an open letter to senators criticizing US decision to stay out of the Syrian conflict, US chiefs of staff commander Gen. Martin Dempsey outlined five options for involvement:
- training, advising and assisting the opposition
- conducting limited strikes
- establishing a no-fly zone
- creating buffer zones inside Syria
- controlling Damascus' chemical arms
Gen Dempsey estimated that the first option would cost about $500m (£325m) a year, while each of the other four actions would require roughly $1bn a month.