US computer network giant Cisco announced it has sued Apple Inc. to stop it from naming its versatile new cellphone iPhone, saying it has owned the trademark for several years.

Cisco's announcement came a day after Apple chief executive Steve Jobs unveiled the iPhone with great fanfare, calling it a "revolutionary product" that can also be used to listen to music, browse the Internet and take pictures.

Cisco said in a statement it had obtained the trademark in 2000 after acquiring Infogear, which owned the iPhone name and had been selling products bearing that name for "several years."

"Cisco entered into negotiations with Apple in good faith after Apple repeatedly asked permission to use Cisco's iPhone name," Mark Chandler, senior vice president and general counsel at Cisco, said in a statement.

"There is no doubt that Apple's new phone is very exciting, but they should not be using our trademark without our permission," he said

The lawsuit, filed in US District Court for the Northern District of California, seeks to prevent Apple from "infringing upon and deliberately copying and using Cisco's registered iPhone trademark," Cisco said in a statement.

"With its lawsuit, Cisco is seeking injunctive relief to prevent Apple from copying Cisco's iPhone trademark," the company said.

Cisco said one of its divisions, Linksys, has been shipping "a new family" of iPhone products since early 2006 and added new ones in December.

"Today's iPhone is not tomorrow's iPhone. The potential for convergence of the home phone, cell phone, work phone and PC is limitless, which is why it is so important for us to protect our brand," Chandler said.

Jobs introduced Apple's iPhone Tuesday at the Macworld Conference and Expo in San Francisco. The new device follows the massive success of Apple's line of iPod music players.

The iPhone will be ultra-slim -- less than half-an-inch (1.3 centimeters) thick -- boasting a phone, Internet capability and an MP3 player as well as featuring a two megapixel digital camera, Jobs said.

Two versions of the iPhone will be released, a four gigabyte version priced at 499 dollars and an eight gigabyte version priced at 599 dollars. The devices will be shipped to US retail stores in June, Jobs said.

Apple expects to make it available in Asia by 2008.

"Every once in a while a revolutionary product comes along that changes everything," Jobs said.

"It's like having the Internet in your pocket," the Apple CEO said. "It's the ultimate digital device. It's like having your life in your pocket."