(CNN) -- NASA's staggering budget shortfall has put its rocket program at "high risk" of missing the planned 2017 launch date for its $12 billion deep-space rocket, a federal watchdog said.
A report by the Government Accountability Office, the investigative arm of Congress, estimates that NASA may need an additional $400 million to meet the December 2017 deadline for launch.
The GAO reports the space agency's Space Launch System program lacks funding and long term focus.
"Without identifying a range of mission possibilities and their required funding, the program is at risk of making uninformed decisions and pursuing development paths that may not make the most efficient use of limited resources in the near term and could negatively impact longer term affordability," the report states.
It acknowledges that NASA metrics indicate the program is on track in terms of design goals, which demonstrate the capability of the system.
In NASA's response to the report, it warned that "delaying the SLS development schedule or diverting funding from other priorities to satisfy a schedule confidence level could jeopardize these goals and result in an increase in costs to the taxpayer."
NASA said the SLS is set to be "the most powerful rocket in history for deep space missions," with hopes of eventually going to Mars.
The office running the program told GAO investigators there is a 90% chance at this time the rocket will not make its launch date.
Orion, NASA's newest manned spaceship, is set to launch on the first SLS test flight, according to the agency's website.
No astronauts will be aboard the December flight, which will test the spacecraft's systems for future manned missions.
If SLS misses its first launch date, NASA has a second flight scheduled for 2021.