Anyone with access to Netflix's online streaming service can effectively increase their movie library by over 2,500 movies, about one thousand of which are available now.

Movies from Starz Entertainment will be available for those with a monthly "unlimited" Netflix subscription, which starts at $8.99 a month.

Customers can also get a Starz Play-only subscription for $7.99 a month.

The addition of Starz titles represents a 20 percent increase to Netflix's own collection, comprised of about 12,000 movies and TV episodes. Users access the films by going to Netflix's website and clicking on the "Watch Instantly" tab on the member homepage. They can then be streamed onto a PC and watched on a monitor or external screen hookup.

The streaming service currently only supports Windows-based use.

Netflix outfared rivals like Comcast and Verizon because it had classic films not offered on their on-demand services. But on-demand firms tend to get new releases sooner. This agreement enables it to compete on that playing field.

Last week Netflix also increased its TV show library through agreements with ABC and CBS, which now permit the online DVD and film-streaming service to syndicate TV shows online.