Bloomberg cited an unnamed person familiar with the matter as saying the Justice Department could file the litigation by the end of the year.
Google did not immediately respond to an AFP request for comment but has held firm that it competes fairly in a very competitive market.
Justice department officials last year sued Google over its dominance in online search and ads, and similar cases have been filed by groups of US states.
US lawmakers advanced blockbuster legislation in June aimed at curbing the power of Big Tech firms with a sweeping reform of antitrust laws, setting the stage for a tough floor fight in Congress.
House Judiciary Committee members approved six bills that take aim at the business practices of Google, Apple, Amazon and Facebook.
One of the bills limits the ability of tech platforms to leverage their control across multiple business lines, potentially opening the door to breaking up some of the giant firms.
The bills are headed to the full House of Representatives, where a contentious debate is expected amid fierce opposition from the tech sector and allies. Any bills would need passage through both the House and Senate and the president's signature.
The outcome of the package remains unclear, with lawmakers from both sides breaking from their party.
