The top U.S. military official is warning that the world risks becoming immune to the escalating global security threats and doing nothing.

Army Gen. Martin Dempsey, chairman of the U.S. Joint Chiefs of Staff, said it would be "a shame" if the world doesn't realize it is reaching a point where it becomes immune or insensitive and shake itself "back into the reality that we can do something about it."

Dempsey said over his 41-year military career he's "never witnessed such significant shifts in the international security environment as we are seeing all around us today."

He told several dozen U.N. ambassadors and military attaches Tuesday that the U.N.'s far-flung peacekeeping operations must keep pace and called for better equipment, rapid response forces, more skilled peacekeepers and international police.