US President Donald Trump said money from his presidential campaign was not used to pay off adult-film star Stormy Daniels. Picture: Reuters/Brendan Mcdermid

Washington - US President Donald Trump said on Thursday money from his presidential campaign was not used to pay off adult-film star Stormy Daniels, publicly acknowledging the payment for the first time and denying any sexual encounter with her years ago.

In a series of early posts on Twitter, Trump said he had reimbursed his lawyer Michael Cohen the $130 000 that Cohen paid Daniels in 2016 as part of a contract for her silence over an alleged one-night stand with Trump in 2006.

"Money from the campaign, or campaign contributions, played no roll (sic) in this transaction," Trump wrote.

His comments come after former New York City Mayor Rudy Giuliani, who joined Trump's legal team last month, said on Wednesday Trump had repaid Cohen the hush money that was given to Daniels.

Trump had told reporters on Air Force One last month that he did not know about the payment to Daniels or the source of the money.

Read more: Trump makes first public comments about Stormy Daniels

The White House has denied that Trump ever had sex with Clifford.

Asked about the latest remarks by Giuliani and Trump, White House spokesperson Sarah Sanders told Fox News on Thursday she could not comment as the litigation was ongoing.

Giuliani, in an interview on Fox News' "Fox & Friends" programme on Thursday, said Trump did not know the details of the arrangement until about 10 days ago, saying the agreement with Daniels was made for personal reasons in an effort to protect Trump's family.

Daniels, whose real name is Stephanie Clifford, has filed two lawsuits against Trump, one to get out of a non-disclosure agreement she had signed in October 2016 just ahead of the November presidential election in exchange for the $130 000, and another for defamation.

Also read: Porn star Stormy Daniels sues Trump for defamation

Asked about the president's tweets on Thursday, her lawyer Michael Avenatti told MSNBC the president had opened himself up to another possible lawsuit for defamation.

"Our case just got exponentially better," Avenatti said. "This is not about sex ... this is about a cover up."

In his posts Thursday, Trump said the 2016 contract was used to stop what he described as "the false and extortionist accusations made by (Daniels) about an affair," and that it had been violated.

Daniels discussed her 2006 encounter with Trump in an interview with CBS News' "60 Minutes" that was broadcast in March.

Avenatti has said that appearance did not violate the agreement because Trump had not signed the contract.