LAKE WORTH, Fla. -- An astronaut who once walked on the moon is causing a stir with claims the government is covering up the truth about aliens and UFOs.

"It's incredible to think that we might be the only intelligent, living system in the universe. That's not credible anymore," Apollo 14 veteran Edgar Mitchell told WPBF-TV in West Palm Beach, Fla., on Friday.

Mitchell's home in a suburb of West Palm Beach is a small shrine to the nine hours and 17 minutes he spent walking on the moon.

Because of his experience, Mitchell's recent comments about unidentified flying objects and aliens are getting a lot of attention.

Mitchell said that he believes the U.S. government has been covering-up the truth for more than 50 years.

"Military pilots, airline pilots, mostly, from all over the world, for 50 years, have reported these things, but they've quit because they're told to shut up and not talk about it by military and intelligence people," Mitchell said.

The 77-year-old said the deception began after the alleged alien landing in Roswell, N.M., in 1947.

Ever since, Mitchell claims, the government has been keeping proof of alien life -- and alien visits -- under wraps.

"Unfortunately, you the press show no interest whatsoever. The giggle factor has been too high. But the science behind it and the research behind it, among the people I know, is accepted. It's real," Mitchell told WPBF.

The issue gained steam earlier this week when Mitchell told a British radio interviewer that he knows that the government knows about life in outer space.

"I've been saying the same damn words for 10 years, almost verbatim, and all of a sudden, here I'm global news," he said.

Mitchell first made global news on Feb. 9, 1971, when his lunar mission earned him a place in the record book for longest moonwalk -- an unbelievable feat that he said could be topped by an alien encounter.

"It would be pretty darn exciting. I have been hoping for that type of experience since I got involved in this," he said.

Mitchell said that he does not know why the government would be covering up the existence of intelligent life.

He said he believes that John F. Kennedy was the last U.S. president to be briefed on UFOs.