Mark Zuckerberg has hit back at Donald Trump after the US president accused Facebook of being "anti-Trump".
Mr Trump's criticism came just days after the social media giant agreed to cooperate with an investigation into the Kremlin's tampering with the US election.
He tweeted that Facebook was "always anti-Trump" and suggested it was in collusion with The New York Times and The Washington Post newspapers.
Mr Trump's Wednesday morning Tweet read: "Facebook was always anti-Trump.The Networks were always anti-Trump hence,Fake News, @nytimes(apologized) & @WaPo were anti-Trump. Collusion?"
But the Facebook CEO and founder defended the network on Wednesday night, saying it broadened debate and gave more people a chance to be heard.
"Trump says Facebook is against him. Liberals say we helped Trump. Both sides are upset about ideas and content they don't like. That's what running a platform for all ideas looks like," he said.
Mr Zuckerberg also said he regrets dismissing allegations that Facebook helped spread misinformation that swayed the election as "crazy".
Campaigns such as Mr Trump's and Democrat opponent Hillary Clinton's spent 1,000 times more on online advertising than any "problematic" adverts uncovered so far, Mr Zuckerberg claimed.
"This is too important an issue to be dismissive. But the data we have has always shown that our broader impact - from giving people a voice to enabling candidates to communicate directly to helping millions of people vote - played a far bigger role in this election," he added.
Last week Facebook announced it would hand over 3,000 adverts purchased by a Russian agency to a US congress investigation.