Armstrong, who inspired a generation to reach for the stars, underwent cardiac bypass surgery earlier after doctors found blockages in his coronary arteries, but he died following subsequent complications. He was 82.

Praising Armstrong as a "reluctant American hero," his heartbroken relatives expressed hope his legacy would encourage young people to "work hard to make their dreams come true, to be willing to explore and push the limits and to selflessly serve a cause greater than themselves."

Armstrong and fellow Apollo 11 astronaut Buzz Aldrin landed on the moon's desolate surface on July 20, 1969.

His first words upon stepping on the lunar surface have since been etched in history, "one small step for man, one giant leap for mankind."

The estimated 500 million people who watched the grainy black and white broadcast breathed a sigh of relief when Armstrong told mission control the module had landed safely, saying "Houston, Tranquility base here. The Eagle has landed."

But the lunar pioneer, who was decorated by 17 countries and received a slew of US honors, was never comfortable with his worldwide fame,

shying away from the limelight. Armstrong even stopped signing memorabilia after learning his autographs were being sold at exorbitant prices.

A "deeply saddened" President Barack Obama on Saturday hailed Armstrong as "the greatest of American heroes, not just of his time, but of all time."

Republican House Speaker John Boehner remembered Armstrong as a "true hero."

Aldrin said he had hoped that he, Armstrong and Michael Collins, the third astronaut on the mission, would have met up in 2019 marking the 50th anniversary of Apollo 11.

"Whenever I look at the moon, it reminds me of the moment over four decades ago when I realized that even though we were farther away from Earth than two humans had ever been, we were not alone," Aldrin said.

Born in Wapakoneta, Ohio on August 5, 1930, Armstrong had an early fascination with aircraft and worked at a nearby airport when he was a teenager.

He took flying lessons at the age of 15 and received his pilot's license on his 16th birthday. Armstrong joined NASA's predecessor agency, the National Advisory Committee for Aeronautics, in 1955.

After retiring from NASA in 1971, Armstrong taught aerospace engineering at the University of Cincinnati for nearly a decade and served on the boards of several companies, including Lear Jet, United Airlines and Marathon Oil.

His family said they had a simple request to people in memory of Armstrong's life.