The top executives of Facebook, Google and Twitter have agreed to testify to Congress in late October, setting up a high-profile showdown between Washington and Silicon Valley days before the 2020 presidential election.

Facebook’s Mark Zuckerberg, Google’s Sundar Pichai and Twitter’s Jack Dorsey each said they would appear before a committee of Senate Democrats and Republicans on Oct. 28 after lawmakers voted earlier this week to subpoena their testimony if they did not agree to appear voluntarily.

Lawmakers have sought to convene the hearing to explore social-media sites’ content-management practices and the future of a federal law, known as Section 230, that spares tech giants from being held liable for the way they police their sites and services.

But the hearing still threatens to evolve into a wide-ranging political clash, particularly as Republicans continue to assail Facebook, Google and Twitter over allegations that they censor conservatives online — charges of political bias they strongly deny.

GOP lawmakers have ramped up their attacks in recent months as tech companies take a more aggressive stand against controversial tweets and posts from President Trump, including his widely debunked comments that seek to cast doubt over the 2020 election. Democrats, meanwhile, widely reject the claims of bias -- instead, they fault Facebook, Google and Twitter for failing to crack down against harmful or abusive posts, photos and videos, including viral election disinformation.

A spokesman for Sen. Roger Wicker (Miss.), the Republican chairman of the Commerce Committee, did not respond to a request for comment. The hearing is set to occur virtually, with the tech executives testifying from the west coast.

Facebook confirmed Zuckerberg would attend, and Google did not comment. Twitter confirmed Dorsey’s attendance in a tweet late Friday that urged lawmakers to be “constructive & focused on what matters most to the American people: how we work together to protect elections.”

“Alleged ‘political bias’ remains an unsubstantiated allegation that we have refuted on many occasions to Congress,” the company added. “It has also been widely disproven by independent research. We do not enforce our policies on the basis of political ideology.”

Lawmakers’ hearing also comes as federal regulators continue to scrutinize Facebook and Google for their expansive corporate footprints. The Justice Department could file an antitrust lawsuit against Google as soon as next week, putting Pichai in the congressional hot seat over the government’s findings at the end of October.