Google must sell its Chrome browser to restore competition in the online search market, US prosecutors have argued.
The proposed breakup has been floated in a 23-page document filed by the US Justice Department.
It also calls for lawmakers to impose restrictions designed to prevent its Android smartphone software from favouring its own search engine.
If the rules were brought in, it would essentially result in Google being highly regulated for 10 years.
Google controls about 90% of the online search market and 95% on smartphones.
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Court papers filed on Wednesday expand on an earlier outline for what prosecutors argued would dilute that monopoly.
Google called the proposals radical at the time, saying they would harm US consumers and businesses and shake American competitiveness in AI.
The company has said it will appeal.
The US Department of Justice (DoJ) and a coalition of states want US District Judge Amit Mehta to end exclusive agreements in which Google pays billions of dollars annually to Apple and other device vendors to be the default search engine on their tablets and smartphones.
Google will have a chance to present its own proposals in December.
A trial on the proposals has been set for April, however President-elect Donald Trump and the DoJ’s next antitrust head could step in.