Democratic Sen. Elizabeth Warren, a 2020 presidential candidate, proposed on Friday a plan to break up Google, Facebook and Amazon, declaring war on the country’s most powerful technology firms and a culture of “weak antitrust enforcement” that allowed them to grow so big.

In a Medium post, the Massachusetts Democrat accused the three firms of using “resources and control over the way we use the Internet to squash small businesses and innovation, and substitute their own financial interests for the broader interests of the American people.”

“To restore the balance of power in our democracy, to promote competition, and to ensure that the next generation of technology innovation is as vibrant as the last, it’s time to break up our biggest tech companies,” Warren wrote.

The proposal is the latest sign that growing public concern with the manner in which so-called Big Tech firms have increased their hold in numerous sectors of the economy — and how they have handled Americans’ data in the process — will feature in the upcoming presidential primary season.

Warren’s announcement came ahead of a campaign rally later Friday in Long Island City, the Queens neighborhood that had been the expected, but recently canceled, site of half of Amazon’s new HQ2.

Warren is not the first Democratic candidate to advocate greater oversight of Silicon Valley and a tougher approach to enforcing antitrust laws, but she is the first to propose a plan to actively break up the three companies. If elected, she said her administration would first support legislation to ban platforms from owning their own separate businesses on those platforms.

“Amazon Marketplace, Google’s ad exchange, and Google Search would be platform utilities under this law,” she wrote. “Therefore, Amazon Marketplace and Basics, and Google’s ad exchange and businesses on the exchange would be split apart. Google Search would have to be spun off as well.”

Second, Warren said she would appoint regulators “committed” to reversing prior mergers, including Amazon’s acquisitions of Zappos and Whole Foods Market, Facebook’s acquisitions of WhatsApp and Instagram, and Google’s acquisitions of Nest, DoubleClick, and Waze.

Google and Amazon did not immediately respond to a request for comment on Warren’s proposal. A spokeswoman for Facebook declined to comment.

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