Faced with soaring crime rates and growing threats from drug trafficking cartels, many countries such as Mexico, Guatemala, Honduras and Bolivia, have turned considerable police duties over to their armed forces.

"On the issues of defense and security, the United States recognizes that sometimes it is difficult to determine whether transnational threats to peace and stability are matters of defense or law enforcement," Panetta said at a pan-American meeting of defense ministers.

"In some cases, countries have turned to their defence forces to support civilian authorities. To be clear, the use of the military to perform civil law enforcement cannot be a long-term solution," the US defense chief stressed.

He said the United States would try to help "bridge the capability gaps between armed forces and law enforcement.

"And we are committed to do so in a manner respectful of human rights, the rule of law, and civilian authority. We can and we will provide a helping hand, but ultimately civilian authorities must be able to shoulder this burden on their own," he added.

Panetta said the United States is backing a Chilean initiative to improve regional cooperation on emergency humanitarian aid and post-natural disaster aid, with data sharing and other cooperation.

After the devastating Haitian earthquake in 2010, regional nations "worked together to provide much-needed help, but we lacked a mechanism to collaborate in real-time and focus our efforts where they were needed most.

"That's what the Chilean initiative is all about rapid and fully integrated response. We should implement that initiative now so that we're ready to respond quickly and effectively when the next disaster strikes," Panetta told his colleagues.

US officials were optimistic this would mark a step forward.

"This will be the first time, we hope, that this conference which started back in 1986, will actually approve something tangible, concrete and actionable. This forum had in the past been one for dialogue and discussion," a senior US officials said, on condition that he not be named.