A U.S. judge on Friday ruled that Apple cannot pursue an injunction against Google's Motorola Mobility Inc., ending a key case for the iPhone maker in the smartphone patent wars.

Judge Richard Posner in Chicago federal court dismissed the litigation between Apple and Motorola Mobility with prejudice, meaning it can't be refiled.

"Apple is complaining that Motorola's phones as a whole ripped off the iPhone as a whole," Posner wrote. "But Motorola's desire to sell products that compete with the iPhone is a separate harm - and a perfectly legal one - from any harm caused by patent infringement."

The ruling is a blow for Apple, as the company expected to gain an upper hand in the smartphone market against Android.

Both parties have the option to appeal Posner's ruling.

The case is Apple Inc. and NeXT Software Inc. V. Motorola Inc. and Motorola Mobility Inc., in the U.S. District Court for the Northern District of Illinois, no. 11-08540.