CAPE CANAVERAL, Florida (CNN) -- President Obama said Thursday that he is "100 percent committed" to the mission of NASA and its future.

Speaking at the Kennedy Space Center, the president sought to try to sell his vision for the space program and assuage workers' concerns about his plan.

Obama's proposal would pump an additional $6 billion into NASA over the next six years, but would pull the plug on a project to send astronauts to the moon.

The White House budget office said the Constellation Program, which had sought to send astronauts back to the moon by 2020, is behind schedule, over budget and overall less important than other space investments.

The administration would instead invest in deep space exploration and scientific development.

White House officials insist that while the president wants to shift priorities, space exploration is not in trouble.

NASA's future, as outlined in the White House documents, would include a multibillion-dollar modernization of Kennedy Space Center, expansion of private-sector and commercial space industries, creation of thousands of jobs and eventually human travel to Mars. Instead of being scrapped as originally proposed, the Orion crew capsule would be used as an emergency vehicle to reach crews at the International Space Station.