According to NASA's Human Space Flight Plans Committee, overseeing the review of the US space agency's exploration plans, budgetary constraints may impede NASA from sending astronauts back to the moon by 2020. Moreover, the challenges entailing the 'Mars Direct" mission may also prevent the agency from sending astronauts straight to Mars.

The ten-member White House panel, created by President Barack Obama, has been assigned the task of figuring out ways in which the government can help NASA overcome pertinent financial and technological issues.

Headed by retired aerospace expert Norman Augustine, the committee will present its preliminary report to NASA Administrator Charlie Bolden and White House science adviser John Holdren on Friday, before the final version is filed for President Obama's review by August end.

Noting that NASA has a budget of nearly $80 billion for human spaceflight through 2020, Augustine said that though a manned Mars mission is the eventual goal, shifting NASA's focus totally on getting there as early as possible is not viable "technically and financially."

Regarding NASA's proposed lunar exploration by 2020, committee member Sally Ride - former astronaut and first American woman in space - said that accomplishing the task would not be possible within the agency's present budget. Ride remarked: "It's very difficult to find an exploration scenario that actually fits within this very restrictive budget guidance that we've been given."