US auditors say NASA doesn't have enough money to start launching its new, $US12 billion ($A12.98 billion) rocket program by the end of 2017 as planned.
The congressional Government Accountability Office on Wednesday issued a report saying NASA's new Space Launch System is at high risk of missing its planned December 2017 initial test flight.
The post-space shuttle program would build the biggest rockets ever to send astronauts to asteroids and Mars.
The report said NASA's own officials told the GAO there is a 90 per cent chance they can't meet the launch date with current funding.
Report author Cristina Chaplain said it's not that NASA has busted its budget for the program because of technical problems. It's just that NASA didn't get enough money to carry out the massive undertaking.
