WASHINGTON — Mark Zuckerberg defended Facebook’s role as a platform for political speech in the 2016 election, after President Donald Trump tweeted out a claim that it was in collusion with other news sources against him.

Zuckerberg also said he regretted saying the notion that so-called “fake news” had an influence on the 2016 election was a “crazy idea.”

“Calling that crazy was dismissive and I regret it. This is too important an issue to be dismissive,” he wrote in a Facebook post on Wednesday.

Trump wrote in a tweet on Wednesday morning that “Facebook was always anti-Trump. The Networks were always anti-Trump hence, Fake News, @nytimes (apologized) & @WaPo were anti-Trump. Collusion?”

His tweet came as Facebook has come under increasing scrutiny as to whether its platform was used by Russian sources to try to influence public sentiment during the campaign. Facebook said it had identified about 3,000 ads linked to Russian sources, and has turned them over to Special Counsel Robert Mueller as well as to congressional committees.

Zuckerberg, however, suggested that the ads in question had to be put into perspective.

“Campaigns spent hundreds of millions advertising online to get their messages out even further. That’s 1000x more than any problematic ads we’ve found,” he wrote.

He also wrote of Trump’s tweet, “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 added that “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.”

CNN reported that the Senate Intelligence Committee has invited representatives from Facebook, Twitter, and Alphabet (parent company of Google) to a Nov. 1 public hearing tied to their investigation of Russian interference in the 2016 election. The House Intelligence Committee announced that they planned to hold a hearing with the major internet companies in the coming month.