Hundreds of negotiators from around the world have descended on Morocco over the past week to finalize a treaty aimed at ensuring that millions of blind and vision-impaired people can get books in accessible formats such as audio, Braille and large print.

But the treaty, years in the making, could be in jeopardy because of unresolved differences between advocates for the blind and the Motion Picture Association of America, which says the accord could undermine protections important for filmmakers, publishers and other major industries.

The agreement, known as the treaty for visually impaired persons, would allow for such books to be distributed internationally, which is now largely prohibited, and encourage governments to allow books to be converted to accessible formats without having to get permission from copyright owners every time.