ALEXANDRIA, Virginia (Reuters) - A Google executive told colleagues the goal for the company's then-nascent online advertising business in 2009 was to "crush" rival advertising networks, according to evidence prosecutors presented at the tech titan's antitrust trial on Wednesday.

The statements underscored the U.S. Department of Justice's claim that Google has sought to monopolize markets for publisher ad servers and advertiser ad networks, and tried to dominate the market for ad exchanges which sit in the middle.

On the third day of the trial, prosecutors began to introduce evidence of how Google employees thought about the company's products at the time when the government alleges it set out to dominate the ad tech market.

"We'll be able to crush the other networks and that's our goal," David Rosenblatt, Google's former president of display advertising, said of the company's strategy in late 2008 or early 2009, according to notes shown in court.

Google denies the allegations, saying it faces fierce competition from rival digital advertising companies.

Rosenblatt came to Google in 2008 when it acquired his former ad tech company, DoubleClick, and left the following year. The notes of his talk showed him discussing the advantages of owning technology on both sides and the middle of the market.

"We're both Goldman and NYSE," he said, he said, according to the notes, referring to one of the world's biggest stock exchanges at the time and one of its biggest market makers.

"Google has created what's comparable to the NYSE or London Stock Exchange; in other words, we'll do to display what Google did to search," Rosenblatt said.

By owning publisher ad servers, the advertiser ad network would have a "first look" at available spots for ads, he said according to the notes. He also said it was a "nightmare" for publishers to switch platforms.

"It takes an act of God to do it," he said, according to the notes.

Rosenblatt, now CEO of online luxury marketplace 1stDibs, did not immediately respond to a request for comment.

Brad Bender, another former DoubleClick executive, who worked at Google until 2022, testified at trial that he forwarded the notes to his team, calling them a "worthwhile read" at the time.

Google has said it is not the only company to offer an integrated suite of products for advertisers and publishers, and that Microsoft, Amazon and Meta Platforms have similar offerings.

If U.S. District Judge Leonie Brinkema finds that Google broke the law, she would consider prosecutors' request to make Google at least sell off Google Ad Manager, a platform that includes the company's publisher ad server and its ad exchange.