The two-day hearing took place more than six months after the conclusion of the trial and a decision is not expected before late summer or autumn.

The case is the first of five major lawsuits by the US government to reach trial, with Meta, Amazon Apple and a separate case against Google also heading for federal courtrooms.

Held in Washington, the trial is the first time the US Department of Justice has faced a big tech company in court since Microsoft was targeted more than two decades ago over the dominance of its Windows operating system.

The decision in the search engine case will be made by US Judge Amit Mehta who presided over several months of testimony late last year that saw Google CEO Sundar Pichai and other top executives take the stand.

At the heart of the government's case is the massive payments made by Google to Apple and other companies to keep its world-leading search engine as the default on iPhones, web browsers and other products.

Court testimony revealed that these payments reach the tens of billions every year to keep its prime real estate on Apple hardware or the Safari and Mozilla browsers.

The US Depart of Justice lawyers allege that Google achieved and perpetuated its dominance -- and strangled rivals -- through these default deals that also expanded to Samsung and other device makers.

On the first day of closing arguments, Judge Mehta focused many of his questions on whether search queries on Amazon, Facebook or Expedia served as competition to Google, one of the key arguments of the tech giant's defense.

Including activity on those websites would put a hole in the US case, which rests on maintaining that general search, in which Google has over 80 percent of the US market share, is the relevant market.

Mehta honed in on Google's contention that DuckDuckGo, the privacy focused search engine, was a competitor.

"You really think that DuckDuckGo is a competitor on Google?" Mehta asked Google's lawyer, who insisted that it was.

Lawyers from the Department of Justice also faced pointed questions from Mehta who pushed back at the government's contention that Google's dominance has stifled innovation for search.

That would be "a hard road for you to go down that Google hasn't innovated enough, how do I make that comparison?" the judge asked.