A US trade authority on Tuesday backed a claim by Microsoft that Motorola Mobility had infringed on its patented technology in Android-powered smartphones.

An initial ruling by International Trade Commission (ITC) administrative law judge Theodore Essex indicated he agreed that Motorola Mobility had tapped into Microsoft technology for scheduling meetings using a smartphone.

Motorola Mobility referred to the decision, which is to be reviewed by the entire commission, a victory since it did not endorse six other patent violation claims by the Redmond, Washington-based software colossus.

"We are very pleased that the majority of the rulings were favorable to Motorola Mobility," said the company's general counsel Scott Offer.

Meanwhile, Motorola has ongoing patent infringement suits against Microsoft in several jurisdictions, including the ITC.

Android has been growing in size as a target, with more than half of the smartphones sold around the world in the third quarter of this year powered by the Google software, according to industry tracker Gartner.

Motorola Mobility's trove of patents was a key reason that Google bought the company this year for $12.5 billion in cash.

"Our acquisition of Motorola will increase competition by strengthening Google's patent portfolio, which will enable us to better protect Android from anti-competitive threats from Microsoft, Apple and other companies," Google chief executive Larry Page said when the Motorola Mobility buy was announced.

Motorola Mobility chief executive Sanjay Jha told financial analysts the US maker of smartphones and touchscreen tablet computers has over 17,000 issued patents and another 7,500 pending.