BOSTON, MA (AP).- After setting a soaring vision to land a man on the moon, President John F. Kennedy struggled with how to sell the public on a costly space program he worried had "lost its glamour" and had scant political benefits, according to a newly released White House tape.

Kennedy and NASA Administrator James Webb hashed out how to strengthen public backing for the mission, such as by highlighting its technological benefits and military uses.

And in a scenario that echoes today, the two worried about preserving funding amid what Webb calls a "driving desire to cut the budget," according to the tape recorded two months before Kennedy was assassinated.

"It's become a political struggle now," Kennedy says, near the end of the 46-minute tape. "We've got to hold this thing, goddamn it."

The Sept. 18, 1963, conversation is among 260 hours of White House recordings that archivists at the John F. Kennedy Presidential Library and Museum have been reviewing in chronological order.

Its release Wednesday comes on the 50th anniversary of Kennedy's May 25, 1961, speech in which he made his famous call to reach the moon by decade's end. While that speech is remembered for its ambition, it also included a caveat that "no single space project in this period ... will be so difficult or expensive to accomplish."

In the tape recorded more than two years later, Kennedy and Webb are heard dealing with that reality. With the 1964 election approaching, Kennedy frets a massive program that's not making obvious advances will prove a liability.

"I don't think the space program has much political positives," Kennedy tells Webb.

The president seems to lament that the rival Russians haven't made the progress in their half of the space race that could bring needed attention to America's program.

"I mean if the Russians do some tremendous feat, then it would stimulate interest again, but right now space has lost a lot of its glamour," Kennedy said.

Webb acknowledges that the tens of billions of dollars spent over a decade made the program a target for lawmakers. But he repeatedly pushes its merits, including spurring technological advances he says will vastly expand the country's economic might.

"I think it's going to generate the technology that's going to make a difference for this country far beyond space," Webb says.

At one point, Kennedy challenges Webb to answer, "Do you think the lunar, manned landing on the moon is a good idea?" The president also asks for and receives assurances from Webb that sending a man to the moon isn't just a "stunt" that will yield the same advances as sending scientific instruments to the moon's surface for billions less.

Kennedy and Webb then agree it's crucial to emphasize the space program's importance to the military and national security, or risk it being considered wasteful.

"The heat's going to go on unless we can say this has got some military justification and not just prestige," Kennedy says.

"I think it's the only way we're going to be able to defend it before the public in the next 12 months," Kennedy says. "I want to get the military shield over this thing."

Maura Porter, a John F. Kennedy Presidential Library and Museum archivist, said the tape offers a look at the pragmatism behind Kennedy's vision for America's future in space. Kennedy's prime motivations for pushing the program were far less practical than what he knew would fly with the public or with Congress, she said.

"He loved the idea of being adventurers and being explorers," Porter said.

Porter said some historians have speculated Kennedy would have backed away from the space program if he won a second term. But the tape indicates he was hoping to be in office when America reached the moon.

On the tape, Kennedy asks Webb if there's any chance the lunar landing will happen during a second term. Webb says no, and the president sounds deflated.

"It's just going to take longer than that," Webb says. "This is a tough job, a real tough job."

Copyright 2011 The Associated Press.