WASHINGTON -- U.S. Democratic presidential candidate John Kerry says he supports a reinvigorated space exploration agenda for NASA but finds fault with the vision U.S. President George W. Bush laid out for the space agency in January.

In written responses to questions submitted to him by Space News and SPACE.com, Kerry criticized the Bush space vision as big on goals but short on resources. Kerry also offered a preview of how NASA’s agenda might change if he is elected president in November.

“NASA is an invaluable asset to the American people and must receive adequate resources to continue its important mission of exploration,” Kerry wrote. “However, there is little to be gained from a ‘Bush space initiative’ that throws out lofty goals, but fails to support those goals with realistic funding.”

The Bush Administration plans to fund a human return to the moon by 2020 by more sharply focusing an only slightly enlarged NASA budget on the new exploration goals. Under the Bush plan, NASA’s $15.4 billion budget would increase about 5 percent a year before leveling out at $18 billion in 2008 and with only rate of inflation increases thereafter. The bulk of NASA’s exploration budget, Bush Administration officials say, would come from money that will be freed up after completion of the international space station in 2010 and from retiring the space shuttle fleet, moves expected to free up about $5 billion to $6 billion a year.

Kerry’s comments were received a day before a presidential commission issued its recommendations for implementing Bush’s vision.

Kerry said that the most immediate impact of the Bush plan is that NASA’s resources are being stretched “even further than they were before the Columbia tragedy,” forcing NASA to make unpopular choices like canceling a space shuttle mission to service the Hubble Space Telescope. NASA is currently seeking industry proposals for servicing Hubble robotically, but space agency officials have made clear that the highest priority of such a mission is attaching a module to Hubble that can be used to guide the space telescope safely into the ocean at the end of its life.

Kerry also criticized the Bush Administration for abandoning the hunt for low cost space transportation, a central goal of NASA during the 1990s.

“The most critical element of our space program should be reducing the costs and increasing the reliability of space transportation to and from low Earth orbit,” Kerry wrote. “This is just one of the many critical areas lost in the Bush initiative.”

Asked what he saw as the most compelling arguments for supporting a civil space program, Kerry cited many of the same economic benefits that Bush articulated in his January speech at NASA headquarters.

“The civil space program acts as an engine of innovation for the entire country, making its enormous benefits hard to quantify but even harder to discount,” Kerry wrote.

Kerry’s emphasis on supporting microgravity research for the sake of improving life on Earth stands in contrast to the Bush Administration’s plans to focus space station research almost exclusively on knocking down the barriers to living and working in space for increasingly long stretches of time.

“I’m excited by potential advances in pharmaceuticals that microgravity could lead to,” Kerry wrote. “Unique drug treatments produced in the microgravity environment may play a vital role in reducing the cost of health care and in developing defenses against chemical and biological terrorist attacks.”

Kerry also defended the space legacy of former U.S. President Bill Clinton -- the last Democrat to occupy the White House. Although the Clinton Administration cut the space agency’s funding, Kerry said NASA still managed to launch and land dozens of shuttle flights, including three servicing trips to Hubble.

Kerry also credited policies pursued under the Clinton Administration with cutting in half the time and money needed to develop space missions, including missions to Mars. And he praised the Clinton Administration for having the foresight to invite Russia into the international space station program, a move, he wrote, “that has allowed us to operate the facility even during the shuttle’s grounding.”

Asked if NASA could expect smaller budgets under a Kerry presidency, the candidate said NASA funding decisions would be weighed against deficit reduction and giving taxpayers the best value for their dollars.

“While reducing the Bush Administration’s reckless deficits will be one of our early challenges, continued investment in a reinvigorated NASA that is innovating, creating jobs, and returning real value to the American taxpayer is what you can expect under a Kerry presidency,” Kerry wrote.

As a fourth-term U.S. Senator from Massachusetts, Kerry is a member of the Senate Commerce, Science and Transportation Committee, which has oversight over NASA’s budget authorization. Kerry has not participated in any NASA hearings since announcing his candidacy in September. Kerry co-sponsored a bill, S.1821, in November to establish a National Space Commission at the White House to coordinate U.S. space activities.

A similar recommendation was made by the Presidential Commission on the Implementation of U.S. Space Exploration Policy, which releases its report today.

Kerry said he continues to seek advice on a variety of high-tech issues from a Science and Technology Committee he established early on in his campaign. That committee, he said, includes “several individuals with a strong background in the civil space arena.” Kerry did not identify his space advisors by name.