SAN FRANCISCO – As Apple Inc.’s iPhone faces stiffer competition in the lucrative market for smart phones, the company is going after one of its main rivals with patent lawsuits claiming theft of touch screen technology and other features.

The complaints cover a slew of models made by Taiwanese phone maker HTC Corp., including the Nexus One, G1 and myTouch 3G – all using the free, rival Android mobile operating software from Google Inc. Non-Android phones include HTC’s Touch series.

But consumers shouldn’t worry about buying or using any of those phones. Patent cases can take months or years to resolve – sometimes longer than the life of these phones – and agreements over licensing and royalty payments often emerge.

Still, it shows Apple’s get-tough strategy as significant competitors emerge.

“We can sit by and watch competitors steal our patented inventions, or we can do something about it,” Apple CEO Steve Jobs said in a statement. “We’ve decided to do something about it.”

Apple said HTC has infringed on 20 of its patents covering aspects of the iPhone’s user interface and hardware.

Google, whose software powers many of the HTC phones, was not listed as a defendant.

When Apple debuted the iPhone in 2007, it changed the smart phone landscape by introducing a stylish, easy-to-use device. Apple is seeking unspecified damages and court orders to block U.S. sales of HTC’s Android phones and other products that Apple says violate its patents.

The complaints were filed with the U.S. International Trade Commission, which has the power to block imports of products and parts made with contested technology, and U.S. District Court in Wilmington, Del., which can award damages and order HTC to stop sales.

In an e-mail, HTC spokeswoman Linda Mills said the company only learned of the lawsuits on Tuesday through media reports and hasn’t had time to review Apple’s claims.