The US government was preparing to sue Google Tuesday in what would be the biggest antitrust case in decades, a judicial source familiar with the matter told AFP.
The Wall Street Journal and New York Times reported earlier that the Justice Department suit will accuse the California tech giant of illegal monopoly behaviour to preserve its dominance in internet search and advertising.
The move comes after months of investigations by federal and state antitrust enforcers seeking to check the power of the massive technology firm and parallel probes into other giants such as Amazon, Facebook and Apple.
It was not immediately clear what remedy the government was seeking in the suit, which could take years to resolve. But it could force changes in business practices or break off segments of the Google empire.
Google and other Big Tech firms have been under pressure from both the political left and right in recent years.
Progressives have claimed the massive firms have stifled competition and worsened economic inequality. Conservatives have accused the internet giants of political bias, although evidence has been scant.
Longtime Big Tech critic Senator Josh Hawley of Missouri said the case would be "the most important antitrust suit in a generation," and welcomed the Justice Department move.