Imports of Xbox 360 hardware to the US could be blocked following a legal victory for Motorola.
The BBC reports that a US International Trade Commission judge has ruled in favour of the firm, ruling that Microsoft has infringed four patents owned by Motorola Mobility relating to video compression and Wi-Fi connectivity.
A full review of the case will be held in August and should that also go against Microsoft the company could theoretically be forced to halt Xbox 360 imports to the US.
Microsoft has previously confessed that should it agree to all of Motorola's demands it would face an annual bill of 2.5bn – a figure its rival disputes.
A Microsoft spokesperson added: "We remain confident the commission will ultimately rule in Microsoft's favour."