Image copyright EPA Image caption Elizabeth Warren is one of 14 people so far vying to be the Democratic candidate in 2020

US Democrat Elizabeth Warren has proposed breaking up tech giants like Amazon, Facebook and Google if elected to the US presidency in 2020.

Seeking to stand out in a crowded Democratic field, Ms Warren told a crowd in Queens, New York, that she was "sick of freeloading billionaires".

Her regulatory plan would reverse some tech mergers and stop companies from competing on their own platforms.

This would promote competition and safeguard small businesses, she said.

Ms Warren pinpointed the Amazon acquisition of WholeFoods as one she would reverse, along with Facebook's merger with WhatsApp and Instagram, and Google's with Waze.

And she said she would halt practices such as Amazon selling on its own Amazon Marketplace platform.

She outlined her proposals in a post on the website Medium. The companies have not yet commented.

Amazon had planned to build a new headquarters close to where Ms Warren spoke but withdrew plans last month, blaming local leaders.

One woman at the rally, who was undecided about who to vote for, said: "What I like is that she's proposing big ideas."

Heard above the din

Analysis by BBC North America reporter Anthony Zurcher

Elizabeth Warren was the first major Democrat to announce a 2020 presidential bid. She's since been joined by five of fellow senators, a current governor, a former governor and an ex-cabinet secretary, among others. Although she came out of the gate first, the pack has quickly caught up.

She's tried to stand out from the crowd by proposing a series of big, detailed progressive policies, including a "wealth tax" on multimillionaires, universal childcare and - in her latest move - using the government's anti-monopoly power to break up big tech companies.

She'll have a chance to make her case for it on Saturday in front of what could be a not-so-welcoming crowd, here at the South by Southwest technology conference in Austin, Texas. Politicians sometimes benefit from taking uncomfortable - and politically risky - stands in front of otherwise sympathetic audiences as a way to show a bit of spine.

There is still a very long road ahead for Ms Warren, and her competitors - many of whom will also be on the Austin stage this weekend. The Massachusetts senator is doing her best to be heard above the din - but so is everyone else.

Who is Elizabeth Warren?

A Massachusetts senator, she has a background in law and policy academia and sits on the progressive left of the Democratic Party.

She burst on to the national scene following the 2008 economic collapse, championing the creation of the Consumer Financial Protection Bureau - a government agency that would serve as a Wall Street watchdog and public advocate.

In 2010, following congressional passage of the Dodd-Frank financial reform bill, she helped the Obama administration set it up.

Two years later, Ms Warren rode that wave of attention to a seat in the US Senate, and on New Year's Eve she became the first major Democratic candidate to announce that she was planning a presidential bid.

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