(Bloomberg) -- U.S. technology giants are headed for their biggest antitrust showdown with Congress in 20 years as lawmakers and regulators demand to know whether companies like Alphabet Inc.’s Google and Facebook Inc. use their dominance to squelch innovation. The House Judiciary antitrust subcommittee is holding a hearing Tuesday on the market power of the largest tech companies. Executives from Apple Inc., Amazon.com Inc., Google and Facebook are testifying. Here’s the latest from the committee room:

Companies argue they face widespread competition (2:56 p.m.)

The four tech giants tried to head off criticism that they dominate their respective markets, as executives in prepared testimony all cited intense competition they say they face from rivals.

Nate Sutton, a lawyer for Amazon, which controls about half of U.S. e-commerce sales, told the House antitrust panel that the company makes up just 4% of U.S. retail sales, with competition from Walmart Inc. and Kroger Co.

Facebook’s Director of Public Policy Matt Perault pointed to competition from Apple, Amazon and Google, among others, in his remarks.

The companies also touted their development of innovative products that have won over consumers and their investment in research and development. Google’s director of economic policy, Adam Cohen, said the company spent $21.4 billion on R&D, three times more than in 2013.

The hearing, led by Democrat David Cicilline of Rhode Island, started at about 3 p.m. Dozens of people were waiting in line to get into the hearing room.

Here’s What Tech Faces in Washington:

The hearing is one of a several that big tech companies face this week in Congress as Washington calls the giants to task for a range of concerns. President Donald Trump is pressuring the companies in Twitter barrages for issues including anti-conservative bias, while the Justice Department and the Federal Trade Commission have taken the first steps toward investigating their conduct. The Justice Department is taking responsibility for scrutiny of Google and Apple, as the FTC oversees Facebook and Amazon.

  • Also on Tuesday, David Marcus, who leads Facebook’s Libra and block chain efforts, heard from disdainful Democrats at a Senate Banking Committee hearing on the company’s proposed cryptocurrency.
  • Trump said Tuesday morning that his administration will look into allegations by billionaire Peter Thiel that Google’s work with China is “seemingly treasonous.”
  • Trump has also said he wants gather tech executives at the White House.
  • Google’s global public policy chief is scheduled to testify Tuesday before a Senate hearing focused on allegations the company engages in censorship.
  • More on tech and antitrust: Did Big Tech Get Too Big? U.S. Joins Europe in Asking: QuickTake

To contact the reporters on this story: David McLaughlin in Washington at dmclaughlin9@bloomberg.net;Ben Brody in Washington at btenerellabr@bloomberg.net

To contact the editors responsible for this story: Sara Forden at sforden@bloomberg.net, Alistair Barr

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