The 50,000 drivers who cruise daily along Interstate 25 between Denver and Colorado Springs drive through ranch and farm land marked by dramatic buttes and the presence of wild animals, a vista that might have been very different but for a little-known federal program.

The Land and Water Conservation Fund, which Congress created in 1965, helped pay for this open space, along with large swaths of land in other areas across the country. But there is a fight looming in Washington as Congress plans to drastically cut the program’s budget, and President Obama, who had accepted cuts in the past, appears ready to oppose them.

The White House has warned it will veto the House Interior spending bill, in part because of its cuts to the conservation fund program. Interior Secretary Ken Salazar said in a telephone interview that the bill would bring conservation “as close to zero as it’s been in modern times.”

The fund is supposed to receive $900 million each fiscal year out of U.S. offshore oil and gas revenue to pay for federal land acquisitions. But with the exception of fiscal 1998, its funding has consistently fallen well short of that mark. The 2011 operating plan provided $300.5 million, and although Obama asked for $900 million for fiscal 2012, the pending House appropriations bill for Interior allocates just under $95 million.

“The cuts that have been made are devastating cuts to conservation,” Salazar said, as he drove through Utah late last month. He added that as he met with oil and gas industry representatives in Utah, “I’ve been reminding them about the importance of the Land and Water Conservation Fund, and there is such an economic return if we invest in conservation.”

But Rep. Rob Bishop (R-Utah), chairman of the Natural Resources subcommittee on national parks, forests and public lands, said Salazar got a “tepid” reception in Utah when he delivered that message and needs to accept the fact that the federal government owns too much land already.

“It is mind-boggling stupid to think the federal government should own one-third of America and not be satisfied with that,” Bishop said in a phone interview. “It’s impossible, when you’re trying to contract the budget and get some savings. Nobody with a straight face can say that we should be expanding our holdings.”

Roughly half of the Land and Water Conservation Fund’s money goes toward federal land acquisition, while the rest goes to state and local grants that support recreation areas, as well as habitat and forest protection.

In part, the program’s obscurity makes it a tempting target for budget cuts. In the 1960s, the idea of tapping oil and gas royalties for conservation attracted the attention of American luminaries such as the writer Wallace Stegner, who helped draft legislative language for the Land and Water Conservation Fund. In 1960, Stegner laid out the reasoning for it in a piece that became known as his “Wilderness Letter.”

“Something will have gone out of us as a people if we ever let the last wilderness be destroyed, if we permit the last virgin forests to be turned into comic books or plastic cigarette cases . . . . And so that never again can we have the chance to see ourselves single, separate, vertical and individual in the world, part of the environment of trees and rocks and soil, brother to the other animals, part of the natural world and competent to belong in it,” he wrote.

But over the years the program — which is often used to buy up isolated parcels of private land within existing parks, refuges and other federal properties, and is combined with matching funds from elsewhere to complete these deals — became less known.

“Nobody’s ever heard of it outside a few dozen people on Capitol Hill,” said Tim Ahern, spokesman for the Trust for Public Land.

Even some congressional Republicans who support the program say its resources are needed elsewhere.

“I’ve seen some great work in terms of what they’ve done in Idaho and other parts of the country in terms of preserving land,” Rep. Mike Simpson (R-Idaho), chairman of the House Appropriations subcommittee on Interior, environment and related agencies, said of the program. But he slashed its funding because he knew Republicans would target it on the floor, and the money would return to the general Treasury. “I didn’t want to put a bunch of money in it that would be taken out.”

And Bishop said if the administration pledged to use the money to address the backlog of maintenance projects on federal land, it “would have a better chance of getting support from us.”

Now the program’s backers are launching a grass-roots drive to enlist Republican support for increased funding. Late last month, the Bull Moose Sportsmen’s Alliance posted two billboards aimed at Colorado Republicans: one in Grand Junction praised Rep. Scott R. Tipton for adding $5 million to the program through a floor amendment, while another in Colorado Springs bashed Rep. Doug Lamborn for trying to zero out the program.

In politically conservative Douglas County, where nearly $2 million from the program helped preserve part of the $105 million worth of land lying between Denver and Colorado Springs, conservative Republicans have demonstrated a willingness to pay for conservation. County residents paid for $21 million in land preservation through a modest sales tax, while proceeds from a state lottery program and money raised by the Conservation Fund, an environmental group, accounted for the rest of it.

Lawrence A. Selzer, president and chief executive of the Conservation Fund, said that in the past six election cycles, at least 75 percent of state ballot initiatives that raised taxes to pay for conservation have passed, even as lawmakers in Congress have become more skeptical of funding land preservation nationwide.

“There’s a disconnect between what voters think and what lawmakers are doing in Washington,” Selzer said.

Still, Obama officials are betting they will get the upper hand in the looming budget battle. On Thursday, Salazar traveled to Albuquerque to announce the first urban National Wildlife Refuge in the Southwest, which will be created through the purchase of a former dairy. Part of the money for the project is slated to come from the Land and Water Conservation Fund’s fiscal 2013 appropriations.

“We will try to get funding from whatever it takes to make it a reality,” Salazar said of the new land acquisition. “Sometimes it takes decades to bring some of these efforts together . . . but you’ve got to start somewhere.”