The US International Trade Commission (ITC) issued a preliminary ruling yesterday backing four out of five Motorola claims that Xbox software infringes its intellectual property.
Administrative law judge David Shaw agreed that the console uses Motorola patented technology for tasks such as efficiently moving video files and connecting wirelessly to the internet.
"Today's recommendation by the administrative law judge is the first step in the process leading to the Commission's final ruling," Microsoft said in an email response to AFP.
"We remain confident the Commission will ultimately rule in Microsoft's favour in this case and that Motorola will be held to its promise to make its standard essential patents available on fair and reasonable terms."
A final ruling from the ITC federal agency is due later in the year.
The regulator could force Microsoft to work out a licensing deal with Motorola Mobility, currently being acquired by Google, or see the Xbox 360 console banned from US stores.
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