SAN FRANCISCO (AP) — Apple fans are amped. The computer and gadget maker is expected to announce a new, more powerful version of its wildly popular smartphone this week — more than a year after it unveiled the iPhone 4.

Last week, Apple Inc. e-mailed invitations to a media event at its headquarters in Cupertino on Tuesday morning. The invite says “let’s talk iPhone,” implying the normally secretive company intends to show off the latest version of the device. In the past, Apple has typically introduced a new iPhone during the summer, but this year it was expected to hold off until the fall.

It has been 15 months since Apple began selling the iPhone 4 last June. The first iPhone was revealed in 2007, and the phone’s signature slick looks, high-resolution screen and intuitive software made it incredibly popular from the start (the rollout of Apple’s iTunes App Store in 2008 helped, too). In addition to gaining millions of fans over the years — 39 million iPhones were sold just between January and the end of June — the iPhone and its large App Store have sparked fierce competition from smartphone makers such as those using Google Inc.’s Android software, which was first rolled out in 2008.