Omarosa Manigault, a staffer for US President-elect Donald Trump, listens as Martin Luther King III speaks to the media after meeting with the President-elect at Trump Tower in New York City on January 16, 2017.

Donald Trump's presidential campaign on Tuesday filed a legal action against former senior White House advisor Omarosa Manigault Newman, alleging she breached a nondisclosure agreement.

Trump's 2020 re-election campaign filed the arbitration with the American Arbitration Association in New York City, according to a Trump campaign official. She is accused of violating a confidentiality agreement she signed with the campaign in 2016, the official said.

Manigault Newman's attorney, John Phillips, told NBC News that "at this time, we haven't seen any legal action filed to date and don't have a comment on it."

A representative for the American Arbitration Association said the group declined to comment, citing its policy to not discuss any arbitrations it may have administered.

Trump himself appeared to reveal the existence of the ex-advisor's nondisclosure agreement in a tweet Monday.

Trump NDA tweet

In an interview with MSNBC's Katy Tur later Tuesday, Manigault Newman said that she has been interviewed by special counsel Robert Mueller, who is investigating Russian interference in the 2016 election.

The president has vented frustration against Manigault Newman during her press tour in the run-up to the release of her new White House expose, "Unhinged: An Insider's Account of the Trump White House," detailing her time advising Trump until she was fired by chief of staff John Kelly in December 2017.

In leaked excerpts and in press interviews, the former contestant on Trump's defunct reality show "The Apprentice" has questioned Trump's mental fitness and alleged the existence of recordings of Trump using racial epithets, including the N-word.