While the iPhone is a cell phone, iPod and Internet device in one, Cisco has been selling a line of iPhone mobile phone products under its Linksys brand since early last year, according to the company.

On the other hand, Apple has had so much commercial success with its "i" series of products -- everything from the iBook, iPod, iTunes to the iSight and iMac -- that the company may have some strength in court using such an argument, Dort said.

Cisco has owned the iPhone trademark since 2000, but it hadn't really used the name until last year, he said. Cisco said it obtained the iPhone trademark after acquiring InfoGear Technology Corp., which sold stand-alone devices to access the Internet without a computer. The original iPhone trademark filing by InfoGear dates back to March 20, 1996, according to Cisco.

One other legal issue stands in the way for both companies, according to Dort. Under U.S. trademark law, a trademark must be renewed every five years. But Cisco didn't file a renewal for the iPhone name within the official five-year time frame. Instead, Cisco filed its renewal application last May, only 12 days before a six-month grace period would have expired.

"The upshot of all that is that Apple...may be preparing a defense that Cisco effectively abandoned the [trade]mark years ago," and that the registration should be canceled, Dort said.