Did the U.S. government have treaties with aliens?

It's no secret that U.S. Presidents weild incredible power and influence, but does that influence go beyond the globe? Nixon, Carter, Truman, Eisenhower, Reagan...what did they know about the existence of UFO's and alien races? Was JFK killed for wanting to share intelligence about UFO's with Russia in hopes of avoiding an accidental war?

#aliens #UFOs #aliencoverup #Roswell