Buzz Aldrin has said he wants to serve as a "strong adviser" in the mission to reach Mars but admitted he doubts it will happen during Donald Trump's presidency.
The second man on the moon attended the Republican's inauguration in January and met with Vice President Mike Pence to discuss space policy last month.
Speaking at a press conference in London marking 60 years of the Omega Speedmaster watch, which he wore when he travelled to the moon, Aldrin said: "I think there's a desire to want to rush and do things and I don't think we can rush and try and get to Mars during his (Trump's) first term or second term."
"I want be a strong adviser working with their people."
Aldrin's manager, Christina Korp also attended the meeting with VP Pence, and said he had appeared "very interested in doing things in space" but added, "We've got to give them some guidance...let's put it that way."
The 87-year-old astronaut, who followed Neil Armstrong on to the moon's surface on July 20 1969, also repeated his desire to see humans colonise Mars.
Asked about Tesla Motors owner Elon Musk's ambitions to organise space travel to the planet, Aldrin said the Florida Institute of Technology had completed a study on Musk's "rather bold plans".
"It's not that easy to do with that large amount of people," he said.
In 2015 Aldrin announced he was teaming up with the FIT to develop "a master plan" for colonising Mars within 25 years.
On Wednesday he said: "I've convinced myself that the purpose of going is to begin to build-up a settlement there and it is the most economic way of proceeding.
He added we should "wait until we go we can do this very confidently and completely not really quick and just go there and come back."
The adventurer said he had fully recovered following his evacuation from Antarctica in December after he became short of breath and showed signs of altitude sickness.