A US Air Force general stated that Area 51 has "secrets that deserve to be protected" at the Air Force Association Air, Space, Cyber conference at National Harbour, Maryland.
General David Goldfein also warned that anyone who plans to storm the secret installation will "see them aliens".
The event went viral on Facebook and Goldfein has been quizzed by reporters on his statement, Daily Star reports.
Goldfein spoke to reporters, revealing: "We're taking it very seriously, our nation has secrets.
"And those secrets deserve to be protected."
Millions of people had planned to attend "Storm Area 51, They Can't Stop All Of Us" on September 20.
Although the event has been deleted on Facebook, thousands of people are still expected to invade the facility in Nevada.
Matty Roberts started the Facebook event as a joke after Joe Rogan interviewed conspiracy theorist and former Area 51 employee Bob Lazar.
On the now-deleted page, it said: "We will all meet up in rural Nevada and coordinate our parties."
"If we Naruto run [in which person runs leaning forward with their arms stretched out behind them], we can move faster than their bullets."
"Let's see them aliens."
US Air Force officials have said that they are standing ready to defend the military base.
Acting secretary of the US Air Force, Matt Donovan, reportedly stated that extra security has been arranged around Area 51.
Area 51 is one of the most secretive locations in the world and is often linked to conspiracy theories about aliens.
US government officials refused to acknowledge the existence of Area 51 for decades.