Alex Jones, on and off

When other platforms such as Facebook banned far-right conspiracy theorist Alex Jones for policy violations earlier in August, for instance, Twitter declined to follow, although it eventually curbed his account's activity temporarily.

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Mr Dorsey has conceded that much his workforce is left-leaning, but Twitter has insisted that its actions reflect its enforcement policies against engaging in threats or other banned behaviour - regardless of the political content.

"Twitter is an incredibly powerful platform that can change the national conversation in the time it takes a tweet to go viral," Representative Greg Walden, who chairs the House panel, said in announcing the testimony. "When decisions about data and content are made using opaque processes, the American people are right to raise concerns."

Mr Walden, an Oregon Republican, said the "committee intends to ask tough questions about how Twitter monitors and polices content".

Representative Kevin McCarthy of California, the No. 2 Republican in the House, said on Friday that "social media platforms are increasingly serving as today's town squares. But sadly, conservatives are too often finding their voices silenced".

He added that after discussions with Mr Dorsey and Mr Walden, "we all agree that transparency is the only way to fully restore Americans' trust in these important public platforms".

Improving Twitter's 'health'

While lamenting abusive conduct on Twitter, Mr Dorsey said in a CNN interview broadcast on August 19 that any move to block content based on political or social views would stoke already rising concern about the power of social-media companies.

Mr Dorsey has declared his intention to improve the "health" of Twitter conversations, including the possibility of placing lower emphasis on follower counts and adding context to misinformation.

Facebook chief operating officer Sheryl Sandberg is also said to be planning to testify to the Senate Intelligence Committee on September 5. In recent days, social media companies have announced removal of accounts with ties foreign countries trying to influence US politics.

We all agree that transparency is the only way to fully restore Americans' trust in these important public platforms.

Alphabet's Google announced it would send senior vice-president for global affairs Kent Walker to the Senate hearing, but the committee's chairman, Richard Burr of North Carolina, said on Thursday that Mr Walker was not sufficiently high up in the company, according to a panel spokeswoman. Senator Burr had requested Google CEO Sundar Pichai. It's currently unclear who will represent Google at the hearing.

Bloomberg