Democratic House Speaker Nancy Pelosi said she was personally skeptical of manned space missions and warned that NASA's future funding could depend on whether it was likely to create jobs.
Pelosi vowed "harsh scrutiny" of all spending requests and said she would be asking "what is the mission? How will the money effectively be spent, in what period of time, to create jobs, compared to what?"
"I, myself, if you are asking me personally, I have not been a big fan of manned expeditions to outer space, in terms of safety and cost. But people could make the case; technology is always changing," she told reporters.
The National Aeronautics and Space Administration's Constellation program aims to send astronauts back to the moon by 2020, and then perhaps to Mars and other destinations in the solar system.
Asked whether she had misgivings about a moon mission, Pelosi replied "the moon would be fine" and said she was "not against the Mars exploration" but added she was skeptical about a manned trip to the red planet.
"There is a debate in the scientific community about the investment that it takes to have those flights be manned -- and I guess we say 'personned' now -- but manned and what the safety of it is," said Pelosi.
Her comments came after US President Barack Obama met with NASA chief Charles Bolden behind closed doors at the White House, reportedly to discuss the space agency's future funding -- which the US Congress controls.
"Everything is in competition for the dollar, and a judgment will be made as to what it does in terms of job creation, because this is what we are doing now," said Pelosi.
The speaker paid tribute to the US moon landing, saying it was "like magic" and underlining "our economy benefited enormously."
"But, again, we have to see dollars well spent creating jobs, accomplishing the mission," said Pelosi.
Explore further: Mars, Saturn and the claws of Scorpius