Microsoft raised objections to Google's plans to buy some 6,000 patents held by bankrupt Nortel Networks over concerns the search giant might change the terms of Microsoft's worldwide, perpetual, royalty-free license to those patents.

Microsoft raised the issue in a filing with a Delaware bankruptcy court, which was reported by Reuters. Microsoft wants its existing agreements to be transferred to Google or any other company that acquires the patents.

Google, which will likely face competing bids, offered more than $900 million for the patent portfolio from the bankrupt Canadian telecom-equipment maker. The patents cover technology that includes wireless video, Wi-Fi, and LTE mobile data technology. Reuters reported that Google would be given the right to terminate Nortel's existing agreements if it acquires the patents.

"Microsoft wants any new owners of the Nortel patents to be subject to Nortel's existing commitments to Standards Setting Organizations and to Microsoft," the company said in a statement. "By making this filing, Microsoft preserves its ability to raise this issue with the bankruptcy court in the event the final buyer of the Nortel assets seeks to disclaim any of these commitments."

Reuters noted that Hewlett-Packard, Nokia and Motorola Mobility also filed objections over the terms of the sale.

Earlier this month, the Wall Street Journal reported that the Justice Department's antitrust division was probing the bidding for the patents. The agency, which found nothing yet to take any action over, is worried that the winning bidder could use the patents to quash competition. The Journal reported that the Justice Department was particularly concerned about Google and Apple winning the bidding.