Motorola's ongoing legal disagreements with Microsoft thickened this morning, with Motorola's mobility unit filing a complaint with the U.S. International Trade Commission over Microsoft's use of patents in its Xbox game console.

While the complaint is currently pending, it could go on to become an investigation by the ITC.

A Microsoft representative said the company is currently reviewing Motorola's filing, and that "we remain confident in our position, and will continue to move forward with the complaints we initiated against Motorola in the U.S. District Court for the Western District of Washington and with the International Trade Commission."

Motorola did not immediately respond to a request for comment.

The move is the latest in what is becoming a back-and-forth between the two companies. In October, Microsoft sued Motorola over use of its patents in Motorola's Android devices. That particular case involved nine of Microsoft's patents.

Microsoft also filed a patent-related lawsuit against Motorola earlier this month over a breach of contract on royalties for the company's patent licenses--specifically, Motorola's patents on wireless networking and video decoders, both of which Microsoft uses in its Xbox 360 game console. According to Bloomberg, which discovered the ITC filing earlier today, Motorola's complaint centers around these same five patents.

The day after Microsoft's royalty-related suit, Motorola countersued with a lawsuit of its own that accused Microsoft of infringing on 16 patents. That also included the Xbox but went on to include other Microsoft products, such as Windows for servers, PCs, and mobile devices.

The ITC has recently been involved in a patent battle between Apple and Nokia, as well as an HTC patent claim against Apple.