WASHINGTON — NASA Deputy Administrator Lori Garver called on a space community divided over canceling the Constellation program to find “common ground,” warning that infighting could jeopardize NASA’s proposed budget growth.

Garver told a Capitol Hill audience March 4 she empathizes with those seeking to save Constellation, a 5-year-old effort to replace the retiring space shuttle with new rockets and spacecraft optimized for lunar missions that U.S. President Barack Obama has proposed terminating. But Garver said continuing Constellation and pursuing the president’s priorities for NASA would cost $5 billion more per year than the roughly $19 billion a year the White House has budgeted for the space agency through the end of Obama’s first term.

“Think of it this way: If you are focused on getting the Constellation budget continued in the future — and I harbor no ill will against those of you who do … but if Constellation is put back in the budget without that $5 billion-a-year increase, where will we cut the budget?” she asked.

Obama’s 2011 spending request calls for increasing NASA’s budget by a total of $6 billion over the next five years and combining that money with savings from canceling Constellation to fund an agenda that includes extending international space station operations through 2020, fostering commercial crew transportation, revitalizing the agency’s network of environmental satellites, investing in green aviation and spending billions on so-called game-changing technologies for future space exploration.

But despite projections of bigger budgets to come, Obama’s decision to scrap Constellation has sparked fierce bipartisan resistance from House and Senate lawmakers.

During her speech, Garver said Obama faced tough choices in ending Constellation.

“The simple fact is that we inherited a system that no longer made sense to continue,” she told industry and government officials attending a breakfast organized by Women in Aerospace here. “We couldn’t afford that system and do all those activities I’ve been talking about. … We cannot do it all.”

Garver warned that infighting imperils NASA’s proposed budget growth an additional $275 million for 2011 followed by three years of better-than-inflation boosts.

“If we are not successful with this budget, I think there is a very real risk that the growth that is proposed in this budget — $19 billion for 2011 — will not be sustained if we aren’t able to come together at some point over the next few months and work toward the common ground,” she said.

Garver made her plea for unity the same day Space News and TheWall Street Journal reported that NASA Administrator Charles Bolden had given Johnson Space Center permission to draft changes to Obama’s NASA proposal aimed at placating lawmakers concerned about bringing an abrupt halt to the development of the Orion Crew Exploration Vehicle and Ares family of rockets.

“I talked to Charlie and he agreed to let us set up a ‘Plan B’ team … to look at what a potential compromise might look like,” Johnson Space Center Director Michael Coats wrote in a March 2 e-mail to several senior human spaceflight managers. “Charlie is meeting with [House Science and Technology Committee Chairman Bart Gordon] in a couple days and asked for a one pager with talking points before his meeting.”

Bolden said March 4 that he did not request anyone at NASA to come up with changes to Obama’s plan.

“The President’s Budget for NASA is my budget. I strongly support the priorities and the direction for NASA that he has put forward,” Bolden said in a written statement. “I’m open to hearing ideas from any member of the NASA team, but I did not ask anybody for an alternative to the President’s plan and budget.”

Bob Jacobs, NASA’s acting associate administrator for public affairs, told Space News March 4 that Bolden is not entertaining alternatives to the president’s plan but is looking for ways to make the most effective use of the $559 million NASA is seeking in 2011 for a new heavy-lift and propulsion research and development program.

“Some people might say, ‘Are you trying to save pieces of Constellation?’” Jacobs said, adding that Bolden’s objective is “to accelerate R&D of heavy lift.”

As Bolden spent part of his week meeting privately with lawmakers to discuss the president’s plan for NASA, some members moved ahead with counterproposals. Sen. Kay Bailey Hutchison (R-Texas), fresh off her gubernatorial primary defeat, introduced legislation March 3 that would require NASA to continue flying the space shuttle through 2012 and keep money flowing to Constellation.

Hutchison’s bill would also require NASA to begin detailed design of a shuttle successor within six months of enactment.

The bill, dubbed the Human Space Flight Capability Assurance and Enhancement Act, authorizes an additional $3.4 billion between 2010 and 2012 for continued  shuttle operations.

Companion legislation is expected to be introduced in the House the week of March 8 by Reps. Suzanne Kosmas (D-Fla.) and Bill Posey (R-Fla.).

Garver, however, said March 4 that it is too late to consider extending shuttle operations much beyond this fall.“The first question I asked when I came back to NASA was could we extend the shuttle,” said Garver, adding that she was told “that time had come and gone that it was not an issue of money at that point, it was an issue of second-tier suppliers, [that] there would be at least a two-year gap between our last flight and the next one, etc.”

Garver said she expects that Congress eventually will get behind Obama’s plan, but admitted change will not come easy for entrenched Constellation supporters.

“I definitely feel that this is the kind of program that there will be broad support [for] over the long run,” she said. “But we did recognize, absolutely, when folks are invested, some literally, in existing programs, it’s very hard for them to see change as positive.”