Donald Trump Casts Doubt on Intelligence Community Over 'So-Called' Russian Hacking

The president-elect tweeted his skepticism.

While the basis of Trump's tweet is that the intelligence briefing was slated for Tuesday and bumped to Friday, a source familiar with the matter tells ABC News that the briefing had always been slated for Friday.

Trump's skepticism is nothing new. On New Year's Eve he expressed a lack of confidence in intelligence officials' findings.

"And so I want them to be sure. I think it's unfair if they don't know," he added. "And I know a lot about hacking. And hacking is a very hard thing to prove. So it could be somebody else. And I also know things that other people don't know, and so they cannot be sure of the situation."

ABC News' Katherine Faulders and Mike Levine contributed to this report.