ALEXANDRIA, Virginia (Reuters) -Alphabet's Google will seek to avoid a forced sale of part of its online advertising business in its latest face-off with U.S. antitrust enforcers at a trial starting on Monday in Alexandria, Virginia.

The trial is the government's next best shot at curbing what a judge has ruled is Google's monopoly power, after losing a separate bid to make Google sell its Chrome browser earlier this month. Online publishers and rival ad tech developers, some of whom have separately sued Google for damages, will be watching the case closely.

The U.S. Department of Justice and a coalition of states are seeking to make Google sell its ad exchange, AdX, where online publishers pay Google a 20% fee to sell ads in auctions that happen instantly when users load websites. The government also seeks to require Google to make the mechanism that decides the winner of those auctions open source.

U.S. District Judge Leonie Brinkema, who will preside over the trial, ruled in April that Google holds unlawful monopolies in web advertising technology. After this week's trial, she will decide what remedies to impose on the company.

The company has asked Brinkema to take the same cautious approach as a judge in Washington, D.C., who recently rejected most of the DOJ's proposals in a separate case over Google's monopoly in online search.

The cases against Google are part of a larger bipartisan crackdown by the U.S. on big tech firms, which began during President Donald Trump's first term and includes cases still pending against Meta Platforms ( META ), Amazon ( AMZN ) and Apple ( AAPL ).

Google says the DOJ's proposal is technically unworkable and would lead to prolonged uncertainty for advertisers and publishers. 

Google had previously offered to sell AdX, however, during private negotiations to end an EU antitrust investigation, Reuters reported last year. Google's internal studies on that potential sale may come into evidence at this week's trial.

Instead of selling AdX, Google has now proposed changing its policies to make it easier for publishers to use and support competing platforms. The DOJ has said such requirements alone are not adequate to restore competition.

A former News Corp executive and executives at DailyMail.com and Advance Local, which operates local news outlets in eight states, are among those expected to testify at the trial.

Some of those witnesses testified last year when the DOJ convinced Brinkema that Google locked publishers into using its publisher ad server - a platform used by websites to store and manage their digital ad inventory - by unlawfully tying the platform to Google AdX.

Doing so allowed Google to engage in practices that were not in publishers' interests, such as giving Google's advertisers the first and last opportunity to bid on ads, Brinkema wrote in her April ruling.

If the DOJ's proposals have not bolstered competition within four years, Google should also be required to sell its publisher ad server, the government said in court papers.