The lack of high-speed Internet access in some areas of the U.S. has been hotly debated, even as that digital divide has narrowed. But a new, wider gap is being created by technology that will make today's broadband feel as slow as a dial-up connection.

Much like broadband enabled downloads of music, video and work files that weren't practical over dial-up, the next generation of Internet connections will allow for vivid, lifelike video conferencing and new kinds of interactive games.

But while access to cable and phone-line broadband has spread to cover perhaps 90 percent of the U.S. in the space of a decade, next-generation Internet access looks set to create a much smaller group of ''haves'' and a larger group of ''have nots.''

The most promising route to superfast home broadband is to extend the fiber-optic lines that already form the Internet's backbone all the way to homes. Existing fiber-to-the-home, or FTTH, connections are already 10 times faster than vanilla broadband provided over phone or cable lines. With relatively easy upgrades, the speeds could be a hundred times faster.

In the U.S., the buildout of FTTH is under way, but it's highly concentrated in the 17-state service area of Verizon Communications Inc., which is the only major U.S. phone company that is replacing its copper lines with fiber. Its FiOS service accounts for more than 1.8 million of the 2.9 million U.S. homes that are connected to fiber according to RVA LLC, a research firm that specializes in the field.

FTTH is also offered by some small phone companies, cooperatives and municipalities, like Chattanooga, Tenn. The other major phone companies, like AT&T Inc. and Qwest Communications International Inc., are laying FTTH in ''greenfield'' developments, but aren't pulling fiber to existing homes. Some cable companies are doing the same.

Graham Finnie, chief analyst for the telecom research firm Heavy Reading, believes 13 percent of U.S. households will be connected to fiber by 2012. Since Verizon is the major builder, the vast majority of those will be in Verizon territory on the East Coast, Texas and California.

''That does beg the question: What happens to everyone else? There's going to be a huge community of people who are not getting FTTH in the next five years,'' Finnie said.

''A quarter of the U.S. is going to get one of the best networks in the world,'' said Dave Burstein, editor of the DSL Prime newsletter.

The rest of the country, he said, is going to be stuck with slow DSL or cable, though the latter is due for upgrades in the next few years that will boost top speeds fivefold.

Still, it's not entirely clear that people on fiber connections are going to have a big advantage over slowpokes on regular broadband. Today, there is not much that can be done on a fast connection that can't be done on a standard one. Fiber is already available to a third of South Korean homes, but that hasn't revolutionized society there, at least not yet.