Facebook CEO Mark Zuckerberg rejects Trump bias claims
Facebook founder Mark Zuckerberg has dismissed comments made by Donald Trump that the site has always been against him.
The US president accused the social network of "collusion" on Twitter, branding it "anti-Trump".
He made the same claim against the New York Times and the Washington Post.
Facebook will shortly hand over 3,000 political adverts to congressional investigators probing alleged Russian meddling in the US election.
The site believes the ads were probably purchased by Russian entities during and after the 2016 presidential contest.
Facebook, Twitter and Google have been asked to testify before the US Senate Intelligence Committee on 1 November about the allegations of Russian interference.
Facebook and Google have confirmed they have received invitations to attend the committee hearing, but none of the social media giants have yet said they will be present.
Dave Lee, BBC North America technology reporter, San Francisco
Mark Zuckerberg has made it clear in the past that he doesn't like Donald Trump - or at least, his policies.
This statement shows frustration, I think. Not just with the president, but at the atmosphere swirling around Facebook at the moment - commentary that is painting it as a burden on the electoral process, and maybe even on society as a whole.
He's trying to show all the good - as he sees it - that Facebook has done.
He feels hard done by. And as a man obsessed by data and metrics, he's probably looking at the problem of Russian-backed fake news ads and seeing it as a minuscule part of all the election goings-on on his network of 2 billion people.
But it's not the scale that's the issue here - but his immature refusal to face up to the public's concerns. It was less cover up, more can't-be-bothered.
Mark Zuckerberg has surely by now realised that he must answer his users' concerns, even when he doesn't share them. His mistake may prove extremely costly - he's boosted those calling for stricter regulation of internet companies.
Follow Dave Lee on Twitter @DaveLeeBBC
In a Facebook post responding to President Trump's criticism, CEO Mark Zuckerberg said he was striving to make "a platform for all ideas". He said that aside from "problematic ads", Facebook's impact ranged from "giving people a voice, to enabling candidates to communicate directly, to helping millions of people vote".
He noted that both ends of the political spectrum were upset about content they disliked, and that liberals in the US had accused him of enabling Mr Trump's victory.
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He said the candidates' campaigns had "spent hundreds of millions advertising online," which he called "1000x more than any problematic ads we've found".
The 33-year-old said he regretted saying on the day Mr Trump was elected that it was "crazy" to say that misinformation on Facebook changed the election's outcome, because it sounded dismissive.
He promised Facebook would "continue to build a community for all people" - and to "defend against nation states attempting to spread misinformation and subvert elections".
Mr Zuckerberg's response attracted 65,000 "likes" within two hours of being posted.
The Kremlin has long denied any form of interference in the US election, and Mr Trump has railed against allegations that his staff had improper links to Russia.
However, US intelligence agencies have concluded Moscow tried to sway the vote in favour of Mr Trump. Congressional committees and an FBI inquiry are currently probing the matter.