https://www.c-span.org/clip/white-house-event/user-clip-reagan-1987-un-speech-alien-threat/4927084

President Ronald Reagan is most famously quoted for suggesting that an “alien threat” from outside the universe would quickly unite humanity and erase our local, worldwide differences. 

He shared this concept on several occasions, most notably during his address to the United Nations General Assembly in September 1987. 

The Core Quotes

1. The UN Address (September 1987)
Reagan famously expanded on the idea of a universal threat while addressing world leaders at the UN: 

“I occasionally think how quickly our differences worldwide would vanish if we were facing an alien threat from outside this world. And yet, I ask you, is not an alien force already among us?” 

2. The Fallston High School Speech (December 1987)
Reagan later shared with students a similar sentiment he had expressed to Soviet leader Mikhail Gorbachev regarding how an external threat could unite humanity.