The U.S. Justice Department has advised a federal judge that it has significant concerns about a proposed legal settlement that would give Google the digital rights to millions of out-of-print books.

The brief filed late Friday in New York federal court marks the first time the Justice Department has publicly shared its thoughts about Google's proposed deal with groups representing U.S. authors and publishers.

Among other things, the nation's top law enforcement agency is worried the agreement will thwart competition in the electronic book market.

Despite its misgivings, the Justice Department told U.S. District Judge Denny Chin it believes Google and its proposed partners can revise the settlement to comply with copyright and antitrust laws.