The agency is worried that the patents could be used to hamper competition in the wireless industry, according to the report.

In April, Google said it had that Nortel is auctioning off as part of its bankruptcy proceedings. While courts in the U.S. and Canada, where Nortel is based, , other interested buyers have until June 20 to counterbid for the more than 6,000 patents.

The DOJ has been reviewing Google's bid but hasn't found competitive issues with it, the Journal reported. However, companies including Apple and Nokia have been rumored to be planning to bid. According to the Journal story, the DOJ's antitrust division is concerned primarily with Apple and the company has been talking with the agency about the concerns.

When Google made its bid for the patents public, it said it wanted the portfolio to create a disincentive for others to sue Google.

Lawsuits are rife in the wireless market, which has experienced explosive growth. Many of the largest hardware and software makers are engaged in patent disputes. Companies that use Google's Android operating system have been popular targets.