SAN FRANCISCO (AP) — Movie rentals are coming to the Internet's most popular video site.

YouTube is making its debut as a rental outlet today to help promote some of the movies that will be shown at the upcoming Sundance Film Festival.

It's part of a test that YouTube hopes will encourage more movie studios to rent movies through its site.

The expansion announced on Wednesday thrusts Google Inc.-owned YouTube into competition with more established vendors such as Apple Inc.'s iTunes store, Amazon.com Inc., Netflix Inc. and Blockbuster Inc.

The first batch of YouTube's rentals will cost $3.99 for a 48-hour viewing period. Movie studios will be able to set their own prices, with rental viewing windows ranging from one to 90 days. YouTube will get an unspecified commission from each rental.