Apple CEO Steve Jobs unsheaths the new MacBook Air during his keynote at the MacWorld Conference in San Francisco. The super-slim new laptop is less than an inch thick and turns on the moment it is opened.

San Francisco ? With an ultra-slim notebook computer and online movie rental service unveiled Tuesday, Apple Inc. is building on surging Macintosh sales and doubling its bet on delivering video to portable devices and televisions over the Internet.

Apple’s foray into the online movie rental business was widely expected, but Chief Executive Steve Jobs surprised some by pulling off alliances with all six major movie studios, including its fierce rival Sony Pictures and Universal, which stopped offering NBC Universal TV shows on Apple’s iTunes Store last fall after a spat over pricing and control.

Users can watch films instantly over a broadband Internet connection or download and keep them for 30 days. They just have to finish watching the movie within 24 hours after starting.

Films will be available through iTunes within 30 days after they’re released on DVD. More than 1,000 will be ready by the end of February, at $2.99 for older movies and $3.99 for new releases, plus $1 for high-definition versions.

The service, which launched Tuesday in the United States and will roll out internationally later this year, will work on Windows-based machines, Macs, iPhones, iPods or Apple TV set-top boxes, which got a significant makeover Tuesday.

Tapping another computer segment, Jobs took the wraps off the MacBook Air laptop and touted it as “the world’s thinnest notebook.” It’s less than an inch thick and is just .16 inches thick at its thinnest point.

Always a showman, Jobs unwound the string on a standard-sized manila office envelop and slid out the ultra-thin MacBook Air. It weighs 3 pounds and comes with an 80-gigabyte hard drive. An option of using a 64GB flash-based solid state drive instead costs $1,000 extra.

The machine does not have an optical drive built in for reading CDs and DVDs. Jobs says consumers won’t miss it because they can download movies and music over the Internet and access the optical drives on other PCs and Macs when they want to install new software.

The new laptop, which has a 13.3-inch screen and full-sized laptop keyboard, will cost $1,799. It goes on sale in two weeks, but Apple is taking orders now.