For years, the Library of Congress has warned that annual budget restrictions are straining its core functions and jeopardizing its numerous programs.

But not many programs get as much attention as the Library’s effort to digitize “talking books” for the blind. Those audiobooks now are on outdated cassettes — a worry for advocates for the blind, who say the players are breaking quickly and need digital replacements.

Today those advocates are expected to crowd a hearing on the Library’s budget, held by the House Appropriations Subcommittee on the Legislative Branch. Their presence will highlight their concern: that appropriators won’t approve enough funding for a four-year digital transition and that Library officials will accept a compromise that provides a six-year plan.

“This is it for blind people,” said Chris Danielson, spokesman for the National Federation of the Blind. “And it’s not just a matter of blind people having reading material for pleasure, it’s often a matter of them having reading material essential for their profession.”

The Library estimates that about 800,000 blind and handicapped people use the system, including a vast majority of the blind population. It’s all on cassettes, for which players are no longer manufactured. As the players break and the cassettes wear out, advocates say, blind readers have few alternatives. Commercial audiobooks are expensive and lack variety; digital players like iPods rely on visual menus and controls.

For 10 years, the Library’s National Library Service for the Blind and Physically Handicapped has been working on a plan to modernize the system. Officials decided on custom-made flash-drive players with cartridges, to be built and implemented with the help of $76 million over four years. Fiscal 2008 was to be the first year.

But instead of the $19.1 million needed for a four-year track, the program received $12.5 million. At that level, the transition will take six years, and there will be fewer books.

And now it looks like the Library has accepted the longer track: For fiscal 2009, Librarian of Congress James Billington is asking Congress for only $12.5 million, said NLS Director Frank Kurt Cylke. Cylke had requested enough to put the program back on a four-year track.

Those two extra years, advocates say, are too long for people whose only options for reading are rapidly deteriorating cassettes and cassette players.

But the budget has been tight for everyone, especially the legislative branch. This year, Congress’ budget only jumped 3 percent — barely enough to keep everything running. The Library got a 10 percent increase from the previous year, but only because it was shortchanged in 2007; taking that into consideration, its budget effectively increased less than 1 percent.

Library spokesman Matt Raymond called the recent budgets “very modest, very limited.” In the past, Library officials have said that soon the restraints will force them to close offices and halt core functions — programs become luxuries.

But blind subscribers say the program is a fundamental literary need. NFB President Marc Maurer said the talking books program is partly responsible for the education of the U.S. blind population, helping them become more successful than their counterparts in other nations. The longer the wait, the fewer books blind people will be able to read, he said.

“I know that in the budget of the United States this is minuscule money, and I know that if the budget of the Library is tight and if the Library wants to have supporters supporting what it needs, that it has a group of supporters,” he said. “I find some of the reaction I get from the librarian positively astonishing in that he’s got a built-in group of hundreds of thousands that mostly he’s been telling, ‘You can’t have books.’”

But whether it takes four or six years, the transition is occurring. The $12.5 million appropriated for fiscal 2008 is enough to start the manufacture of the digital players and cartridges. So far, the National Library Service has received proposals from manufacturers and hopes to start production soon, Cylke said.

By the end of this year, officials hope to start phasing out cassette players for the custom digital players.

But blind readers say they are worried that the slow transition will decrease the number of books to which they have access. They have some support from Members. Rep. Edolphus Towns (D-N.Y.) has asked his colleagues to sign a letter pushing for more funding.

Blind patron Terri Uttermohlen said she now uses commercial equipment because of the increasing problems of the Library’s cassettes and players. But most blind people can’t afford that expense, she said, and it limits the variety of material. Her sister, who also is blind, complains of cassettes that suddenly break down in the middle of a book. That can mean a perpetual cliffhanger or the loss of needed information.

“It’s really important that when people are talking about funding public policy, that they take into account how important a year can be or how important a day can be to people who use a service,” she said. “A lot of people can pick up a newspaper or go to the bookstore. It’s not out there for us.”