Adult film actress Stormy Daniels is suing US President Donald Trump for defamation, saying he lied by tweeting that her claim of being threatened if she discussed an alleged sexual encounter with him was a "total con job."
The lawsuit in federal court in Manhattan escalates Daniels' litigation with Mr Trump and his personal lawyer, Michael Cohen, who paid her $US130,000 (NZ$184,000) before the 2016 US presidential election to keep quiet about the alleged sexual encounter a decade earlier.
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Mr Trump's lawyers and the White House did not immediately respond to requests for comment.
Mr Trump used Twitter on April 18 to complain about a composite sketch that Daniels' lawyer Michael Avenatti released the prior day.
That sketch depicted a man Daniels said assailed her in a Las Vegas parking lot soon after she had agreed in May 2011 to work with In Touch magazine on a story about her relationship with Mr Trump.
"A sketch years later about a nonexistent man," Mr Trump wrote. "A total con job, playing the Fake News Media for Fools (but they know it)!"
In her complaint, Daniels said the assailant had urged her to "leave Trump alone" and "forget the story," and after looking at her infant daughter said:
"That's a beautiful little girl. It'd be a shame if something happened to her mom."
Daniels said the president knew his tweet was false or made it with reckless disregard for its truth, and falsely accused her of making up the assailant.
"By calling the incident a 'con job' Mr. Trump's statement would be understood to state that Ms Clifford was fabricating the crime and the existence of the assailant, both of which are prohibited under New York law," Daniels said.
Mr Trump has 51.4 million Twitter followers.