Top executives from Facebook Inc and Twitter Inc will defend their companies in the US Congress on Wednesday over what lawmakers see as a failure to combat continuing foreign efforts to influence US politics.
Facebook Chief Operating Officer Sheryl Sandberg, who will testify alongside Twitter Chief Executive Jack Dorsey, will acknowledge to the Senate Intelligence Committee that the company was too slow to respond to Russian efforts to interfere in the 2016 US election and American society, but insist it is doing better.
"We've removed hundreds of pages and accounts involved in coordinated inauthentic behaviour — meaning they misled others about who they were and what they were doing," Ms Sandberg said in written testimony released on Tuesday.
Facebook, Twitter and other technology firms have been on the defensive for many months over political influence activity on their sites as well as concerns over user privacy.
Their executives have travelled to Washington several times to testify in Congress, including 10 hours of questioning of Facebook Chief Executive Mark Zuckerberg over two days in April.
The Senate Intelligence Committee has been looking into Russian efforts to influence US public opinion throughout President Donald Trump's presidency, after US intelligence agencies concluded that entities backed by the Kremlin had sought to boost his chances of winning the White House in 2016.
Moscow denies involvement, and Trump — backed by some of his fellow Republicans in Congress — has repeatedly dismissed investigations of the issue as a partisan witch hunt or hoax.
Some Republicans have also charged social media companies with bias against Trump and other conservatives. Twitter's Mr Dorsey was to follow his Senate testimony on Wednesday morning with an appearance at an afternoon hearing looking at that issue in the House of Representatives.
Mr Dorsey will tell the House Energy and Commerce Committee that Twitter "does not use political ideology to make any decisions," according to written testimony also made public on Tuesday.
Trump faulted Twitter on July 26, without citing any evidence, for limiting the visibility of prominent Republicans through a practice known as shadow banning.
Last week Trump accused Google's search engine of promoting negative news articles and hiding "fair media" coverage of him, vowing to address the situation without providing evidence or giving details of action he might take.
Republicans control majorities in both the Senate and House, but the House's approach to the election issue has been far more partisan than in the Senate.
In the Senate, both the Republican Intelligence Committee chairman, Richard Burr, and Democratic vice chairman, Mark Warner, said they called Wednesday's hearing to press the social media companies to do more.
They also asked Alphabet Inc's Google to send a top executive to testify, but declined its offer to dispatch Chief Legal Officer Kent Walker rather than Alphabet Chief Executive Larry Page, saying it wanted a top corporate decision-maker.
Google did release written "testimony" from Walker ahead of the hearing, even though he was not expected to appear. Like Ms Sandberg, Mr Walker said in his statement that the company was taking the issue of foreign interference in politics very seriously.