Google Inc plans to build a handful of experimental, ultra-fast broadband networks around America to connect consumers to the Internet and ensure that tomorrow's systems can keep up with online video and other advanced applications that the search company will want to deliver.

The Google project, announced on Wednesday, is also intended to provide a platform for outside developers to create and try out all sorts of cutting-edge applications that will require far more bandwidth than today's networks offer.

The company said its testbed fiber-optic networks will deliver speeds of 1 gigabit per second to as many as 500,000 Americans. That would be roughly 50 to 300 times faster than the DSL, cable and fiber-optic networks that connect most American homes to the Internet today, at speeds typically ranging from 3 megabits to 20 megabits per second.

Google envisions systems that will enable consumers to download a high-definition, full-length feature film in less than 5 minutes; allow rural health clinics to send 3D medical images over the Internet; and let students collaborate with classmates around the world while watching live 3D video of a university lecture.

"Our goal is to trial new technologies and figure out what kinds of applications you can send over these big pipes," said Richard Whitt, Google's Washington-based counsel for telecommunications and media. "There may be next-generation applications that are being held back right now."