Twitter's CEO will also face angry Republicans who claim the companies have shown evidence of bias against conservatives. In prepared testimony released ahead of a House hearing Wednesday afternoon, Jack Dorsey says his company does not use political ideology to make decisions.

Congress has sharply criticized the social media companies over the last year as it has become clear that they were at the forefront of Russia's interference in the 2016 elections and beyond. That scrutiny has led to additional criticism over the companies' respect for user privacy and whether conservatives are being censored — frustrations that are particularly heightened ahead of the midterms.

"The companies have made progress, the government has made progress, but the bad guys have made progress as well," said Virginia Sen. Mark Warner, the top Democrat on the Senate intelligence committee, which will hear from both companies in the morning on the subject of foreign interference. Warner has proposed a series of ways the companies could be regulated for the first time.

The afternoon hearing in the House Energy and Commerce Committee will feature only Dorsey in a hearing focused on bias and the platform's algorithms. Some Republicans, including President Donald Trump, have pushed the idea ahead of the elections that Twitter is "shadow banning" some in the GOP because of the ways search results have appeared. Twitter denies that is happening.

Missing from the conversation will be Google, which refused to make its top executive available for the Senate intelligence hearing. The panel invited Larry Page, the CEO of Google's parent company, Alphabet, but the company said it would send a lower-ranking executive instead. The committee rejected that offer, and is expected to have an empty chair at the hearing for Page.

Senate Intelligence Committee Chairman Richard Burr said Tuesday that Google doesn't "understand the problem" if it doesn't want to work with the government to find solutions.

The back-and-forth with Google is the latest in a year's worth of attempts by Congress to force the companies to focus more sharply on the Russian interference issue. While Burr says he believes Facebook and Twitter do understand the problem, it took both companies several months last year to acknowledge they had been manipulated.

It also underscores how difficult the problem may be to solve. While the companies have made many changes around their policies and have caught and banned hordes of malicious accounts over the past year, their business models — free services that rely on attracting as many users as possible for as long as possible and finding out as much about them as possible — remain the same. Some critics have charged that unless they change this, they will continue to contend with bad actors taking advantage of their systems.

In prepared remarks for Wednesday's hearing, Facebook's No. 2 executive, Sheryl Sandberg, details many ways the company is addressing the problem but reiterates that the company was slow to spot it. Thirteen Russians were indicted by special counsel Robert Mueller earlier this year on charges of an elaborate plot to disrupt the 2016 U.S. presidential election by creating fake accounts that pushed divisive issues on social media.

In her testimony, Sandberg details ongoing efforts to take down material linked to the Russian agency, including the removal this year of 270 Facebook pages. Still, Sandberg says the company's overall understanding of the Russian activity in 2016 is limited "because we do not have access to the information or investigative tools" that the U.S. government has.

"This is an arms race, and that means we need to be ever more vigilant," Sandberg says.

Dorsey says Twitter has continued to identify accounts that may be linked to the same Russian internet agency in Mueller's indictment. He says Twitter has so far suspended 3,843 accounts the company believes are linked to the agency, and has seen recent activity.

On bias, the Twitter CEO is aggressive in defending his company, saying in the prepared House testimony that he wants to be clear about one thing: "Twitter does not use political ideology to make any decisions, whether related to ranking content on our service or how we enforce our rules."

To address the concerns, Dorsey offers an explanation of how Twitter uses "behavioral signals," such as the way accounts interact and behave on the service. Those signals can help weed out spam and abuse.

He says such behavioral analysis "does not consider in any way" political views or ideology.

Dorsey says the San Francisco-based company is also "committed to help increase the collective health, openness, and civility of public conversation, and to hold ourselves publicly accountable towards progress."

Only Dorsey was invited to the House hearing after specific Republican concerns about bias on Twitter. While all three tech companies have been accused of political bias against conservatives, the more public-facing nature of Twitter has made it an especially easy target.

Despite the companies' denials, conservatives have continued to push the issue ahead of the 2018 elections.

"Sadly, conservatives are too often finding their voices silenced," House Majority Leader Kevin McCarthy said in a statement when the hearing was announced. "We all agree that transparency is the only way to fully restore Americans' trust in these important public platforms."