Buzz Aldrin and Michael Collins have urged NASA to scrub its lunar ambitions and set its sights on Mars, the BBC reports.
Speaking at an Apollo 11 reunion of the pair and Neil Armstrong at Washington DC's National Air and Space Museum, marking the 40th anniversary of the first Moon landing, Collins said: "I worry that the current emphasis on returning to the Moon will cause us to become ensnared in a technological briar patch, needlessly delaying for decades the exploration of Mars - a much more worthwhile destination."
Aldrin, who recently roundly condemned the current NASA plan to return to the Moon by 2020 as "a glorified rehash of what we did 40 years ago", said: "Apollo 11 is a symbol of what a great nation and a great people can do if we work hard, work together and have strong leaders with vision and determination.
"The best way to honour and remember all those who were part of the Apollo programme is to follow in our footsteps; to boldly go again on a new mission of exploration."
Their call is backed by former White House spokesman Bob Weiner and policy analyst Zoe Pagonis, who last Friday released a statement calling on NASA to "focus on the dream of travelling to other planets and reverse [its] satisfaction with the mundane".
The pair said: "The news for NASA now is a pale comparison to 1969. Forty years later, we have to ask, what happened to man and woman on Mars and Venus? By now we thought we'd even reach Pluto."
They added: "Commuter shuttles to a space station close-in and use of robots have been a sad substitute. It wasn't and isn't all we can do - we saw that's nonsense with our own eyes. Man on the Moon was the most profound scientific achievement of our lifetimes - and was too long ago."
While NASA has pulled out all the stops to celebrate its 40th lunar anniversary, it is arguably bogged down in the expensive Constellation programme, which promises little more than the "glorified rehash" of past triumphs.
Neil Armstrong, though, was on hand to remind the Washington audience of just how great an achievement the Apollo programme was. He said: "It was the ultimate peaceful competition: USA vs USSR. I'll not assert that it was a diversion which prevented a war, nevertheless it was a diversion.
"Eventually, it provided a mechanism for engendering co-operation between former adversaries. In that sense, among others, it was an exceptional national investment for both sides." ?