The White House said Wednesday that President Trump previously has won an arbitration case against adult film star Stormy Daniels, who alleges an affair with Mr. Trump and is suing him.

“The president has denied the allegations against him, and again this case has already been won in arbitration,” said White House press secretary Sarah Huckabee Sanders.

She would not elaborate and referred questions to Mr. Trump’s private lawyer.

Ms. Daniels’s attorney, Michael Avenatti, responded mockingly to a reporter from The New York Times, saying of the White House’s claim that Mr. Trump won in arbitration, “Yeah, and he also won the popular vote.”

Ms. Daniels, whose real name is Stephanie Clifford, has filed a lawsuit against Mr. Trump in California, seeking to declare that a nondisclosure agreement between them is not valid because Mr. Trump never signed it.

The complaint alleges that Ms. Daniels had a relationship with Mr. Trump between 2006 and 2007.

Lawrence Rosen, a lawyer who represents Trump lawyer Michael Cohen, said in a statement on Wednesday that Mr. Cohen obtained an arbitrator’s order prohibiting Ms. Clifford from disclosing confidential information pertaining to the nondisclosure agreement.

During the 2016 presidential campaign, Ms. Daniels said, Mr. Cohen “aggressively sought to silence” her, including a payment of $130,000.