WASHINGTON (Reuters) - Facebook Inc FB.O said on Monday that it had not been invited to a White House summit on social media being held later this week.

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The White House has repeatedly declined to say who will attend the July 11 event. White House spokesman Judd Deere said last month the meeting would “bring together digital leaders for a robust conversation on the opportunities and challenges of today’s online environment.” He said on Monday that Trump will speak at the event.

Several conservatives on social media have said they are attending the summit, including Bill Mitchell, a Trump supporter who hosts an online show. At least two social media users posted photos of an invitation to the summit that said it will take place at 3 p.m. EDT (1900 GMT) on Thursday.

U.S. politicians, led by Trump, have increasingly used social media to try to woo voters directly. Trump has said on many occasions that he would not have been elected without Twitter TWTR.N and Facebook.

But Republican Trump has regularly attacked Facebook and Twitter as being “biased” in favor of Democrats, without offering evidence. He suggested in a Fox Business Network interview last month that Twitter made it “very hard for people to join me at Twitter... and they make it very much harder for me to get out the message.”

In March, Trump tweeted that “Facebook, Google and Twitter, not to mention the Corrupt Media, are sooo on the side of the Radical Left Democrats. But fear not, we will win anyway, just like we did before!”

All three companies have denied political bias.

When asked if it had been invited to Thursday’s meeting, a spokesman for Facebook said in an emailed reply that it had not.

Twitter declined to say on Monday if it had been invited to the summit or would take part. Alphabet Inc's Google GOOGL.O unit did not immediately respond to a request for comment on whether it had been invited.

In April, Trump met with Twitter Chief Executive Jack Dorsey and spent a significant time questioning him about why he had lost some Twitter followers, a person briefed on the matter told Reuters. With more than 61 million followers, Trump has one of the most-followed accounts on Twitter.