WASHINGTON, United States - US President Donald Trump broke a 2 month silence Thursday about allegations he slept with a porn star, insisting that he did not pay her $130,000 hush money.

Trump offered a flat "no" when asked if he knew about the payment that was made by his lawyer shortly before the 2016 election.

The actress, Stephanie Clifford -- who goes by the screen name Stormy Daniels -- claims it was money paid to cover up a tryst more than a decade ago.

Trump's long-time lawyer Michael Cohen has admitted to making the payment, but has not indicated why he made it.

He has accused Daniels of breaching a non-disclosure agreement.

Trump said he did not know why Cohen made the payment. "You'll have to ask Michael Cohen. Michael is my attorney. You'll have to ask Michael."

Asked if he knew where the money came from, Trump told reporters on Air Force One, "No, I don't know."

That claim was immediately challenged by Daniels' lawyer Michael Avenatti.

"We very much look forward to testing the truthfulness of Mr. Trump's feigned lack of knowledge concerning the $130k payment," he tweeted.

"As history teaches us, it is one thing to deceive the press and quite another to do so under oath."