The White House has denied that Trump had sex with Daniels, whose real name is Stephanie Clifford. Daniels has said she and Trump had sex once in 2006.
Asked why his lawyer, Michael Cohen, paid the money if the allegations were untrue, Trump told reporters on Air Force One, "You'll have to ask Michael Cohen. Michael's my attorney."
Asked if he knew about the payment to Daniels, Trump said "No."
Asked if he knew where the money came from to pay Daniels, Trump told reporters, "No, I don’t know."
Cohen has said he paid Daniels out of his own pocket.
Last month, Daniels sued Cohen to be released from the non-disclosure agreement she signed in October 2016 in exchange for the $130,000 payment from him.
Daniels' attorney, Michael Avenatti, said Trump's admission that he did not know about the agreement bolstered his client's case to be released from the deal.
"Good (actually GREAT) things come to those who wait!!! The strength of our case just went up exponentially. You can't have an agreement when one party claims to know nothing about it," Avenatti said on Twitter.
Avenatti has said he wants to question Trump and Cohen about the agreement, which was signed the month before Trump was elected president.
"We very much look forward to testing the truthfulness of Mr. Trump's feigned lack of knowledge concerning the $130k payment as stated on Air Force One," Avenatti tweeted. "As history teaches us, it is one thing to deceive the press and quite another to do so under oath."
Last week, a federal judge said Avenatti's request to depose Trump and Cohen was premature.
Cohen wants to force Daniels to use arbitration, as opposed to open court, to settle the dispute over the agreement.
In an interview that aired last week, Daniels told CBS's "60 Minutes" program that she and Trump had sexual relations only once, but he had kept in touch with her. She said she was not attracted to Trump, who was 60 at the time. Daniels was 27 in 2006.
In filings with the U.S. Justice Department and Federal Election Commission, watchdog groups have said the payment amount may have exceeded campaign contribution limits and violated U.S. law.
A former Playboy model, Karen McDougal, has described having a 10-month affair with Trump, also starting in 2006, which the White House has said Trump denies.
(Reporting by Jeff Mason; Writing by Eric Beech; Editing by Peter Cooney and Alistair Bell)