In what can be seen as a preemptive strike against Apple, which is expected to announce it will enter the movie-rental business at tomorrow’s MacWorld expo, Netflix will begin offering unlimited online movie streaming from a library of over 6,000 movies to customers with unlimited DVD-rental plans.

Until now, Netflix had limited the number of hours of video accessed via the website that it made available to subscribers under a regular subscription plan. For example, customers with the $16.99 per month plan could watch up to 17 hours of streaming video per month. The unlimited streaming option could become much more relevant after the forthcoming Netflix-LG branded set-top box debuts later this year, which will let subscribers watch movies and TV shows directly on their TVs.