Although specifics of President Obama's NASA budget won't be released until Monday, a bipartisan group of legislators representing key space centers vows to fight to preserve the agency's besieged moon program.

In its fiscal year 2011 budget request, the White House reportedly plans to scrub the Constellation moon program and put up $6 billion over the next five years to help along private companies as they develop spacecraft to take humans to low Earth orbit.

The proposal would be a major change for NASA, which has operated U.S. government human spacecraft for nearly 50 years.

Although space officials and commercial advocacy groups say the strategy shift would invigorate new industries and potentially create thousands of jobs, members of Congress are lining up opposing Obama's plan.

The voices are especially coming from districts and states with significant NASA interests.

Sen. Bill Nelson, D-Fla., says he is "hopeful" for a more "robust" space program.

"We're going to have to get the president to do more for NASA," Nelson said. "America's global leadership in science and technology is at stake if we don't maintain a more robust space exploration program."

Representatives from the Space Coast are also weighing in.

Rep. Bill Posey, R-Fla., is asking for a temporary extension to the space shuttle program, but that goal may face its own difficulties with the orbiters' retirement rapidly approaching later this year.

"I will continue to work with my House colleagues from both parties and from across the country to keep America first in space," Posey said in a statement. "This issue is far from over."

Posey said he fears the plan represents a "slow death" of the space program.

With the approaching gap in U.S. human spaceflight capabilities, the White House plan threatens "to turn the gap into an abyss with no end in sight," said Rep. Suzanne Kosmas, D-Fla.

The Ares rockets and Orion spacecraft of the Constellation program have suffered repeated delays in the last few years, widening the worrisome gap.

"The Space Coast and communities across the country have been looking to the President for leadership and a bold vision for the future of space exploration, and after months of delays he seems to be falling short. It is simply unacceptable and I will fight back, along with my colleagues from both parties, to maintain a robust space program and to preserve as many Space Coast jobs as possible," Kosmas said.

Kosmas also supports adding more shuttle flights if there is no specific replacement craft outlined in the budget.

"I agree with extending use of the International Space Station and I am a strong supporter of commercial spaceflight, but I do not think we can rely on commercial flights alone for access to space and the ISS," Kosmas said.

Members of the Texas congressional delegation are also joining the chorus of lawmakers opposing the reported plan.

"I strongly urge the President to reconsider any attempt to reduce the role of human space flight at NASA," said Rep. Pete Olson, R-Texas. "But Congress also has an important role in the decision making process and I will be working steadfastly with my colleagues to ensure that this short sighted proposal is not the final answer on the future of NASA."

Olson represents thousands of workers at the Johnson Space Center in Houston, the home of the NASA astronaut corps and mission control.

Sen. Kay Bailey Hutchison, R-Texas, said she would "strongly oppose any further cuts" to the human space program that would make the United States dependent on other countries for access to orbit.

The House Subcommittee on Space and Aeronautics, chaired by Rep. Gabrielle Giffords, D-Ariz., plans a hearing next week with NASA watchdogs two days after the budget unveiling.

Giffords is the wife of a current NASA astronaut and a critic of turning over space travel to commercial providers.

In an October statement, Giffords said Congress has "stressed the importance of a robust technology development program as well as engagement of the commercial sector as appropriate -- recognizing the potential of the commercial sector to support NASA's low Earth orbit activities in the future, but also making clear that we are not prepared to have our astronauts' access to space held hostage to purchases of seats from non-existent commercial providers."