US President Barack Obama will today formally propose abandoning plans to return US astronauts to the moon, by ending the costly Constellation next-generation rocket program.
Arguing it must trim spending in tough times, the administration will instead direct NASA to turn to long-range research and development which could eventually lead to a manned space program to Mars, a senior US official said.
"We are cancelling the program, not delaying it," Obama's budget chief Peter Orszag told reporters.
The decision will mean that NASA will be constrained to low-earth orbits for years to come, and will transform the aspirations of the US space program following the planned retirement of the Shuttle fleet in September.
Under the new plan, Obama will also propose boosting the development of commercial rockets and other vehicles that can ferry US astronauts to the International Space Station (ISS), an outside US government advisor said.
The Constellation program was launched in 2004 by then-president George W Bush after the Columbia space shuttle mission ended in disaster with the death of all seven crew members in 2003.
NASA has faced growing pressure to cut its budget as the US government's debt soars and the United States buckles under the deepest economic crisis since the Great Depression of the 1930s.