Top NASA officials and former astronauts praised the late Neil Armstrong on Saturday, saying he made a major mark on space exploration.

"When I think of Neil, I think of someone who for our country was dedicated enough to dare greatly," John Glenn, the the first American to orbit the Earth, said in an interview with the Associated Press. "He showed a skill and dedication that was just exemplary. I'll miss him not only for that but just as a close personal friend."

NASA administrator Charles Bolden added in a statement: "As long as there are history books, Neil Armstrong will be included in them. Besides being one of America's greatest explorers, Neil carried himself with grace and humility that was an example to us all."

Armstrong became the first person to set foot on the moon, on July 20, 1969, when he said: "That's one small step for man; one giant leap for mankind."

The grainy black-and-white television images of him taking his first lunar stroll were watched by an estimated 600 million people worldwide and firmly established him as one of the great heroes of the 20th century.

Armstrong, who had heart surgery in early August, died Saturday in Cincinnati at 82, said NASA spokesman Bob Jacobs. The cause was complications from cardiovascular procedures, his family announced.

PHOTOS: Neil Armstrong | 1930-2012

He was never comfortable with celebrity he saw as an accident of fate, for stepping on the moon ahead of fellow astronaut Edwin "Buzz" Aldrin. The reticent, self-effacing Armstrong would shun the spotlight for much of the rest of his life.

In a rare public appearance, in 2000, Armstrong cast himself in another light: "I am, and ever will be, a white-sock, pocket-protector, nerdy engineer."

See more here:

Neil Armstrong remembered by John Glenn, NASA head