US President Donald Trump’s personal lawyer says he paid $US130,000 $166,000 out of his own pocket to a porn actress who allegedly had a sexual relationship with Mr Trump in 2006.

Michael Cohen said in a statement to The New York Times he was not reimbursed by the Trump Organisation or the Trump campaign for the payment to Stormy Daniels, whose real name is Stephanie Clifford.

Mr Cohen wrote: “The payment to Ms Clifford was lawful, and was not a campaign contribution or a campaign expenditure by anyone.”

He told the Times he had delivered a similar statement to the Federal Election Commission (FEC) in response to a complaint filed by Common Cause, a government watchdog group.

Common Cause had asked the FEC to investigate the source of the $US130,000 payment and to determine whether it represented an excessive campaign contribution.

Mr Cohen told the Times: “The allegations in the complaint are factually unsupported and without legal merit.”

The Wall Street Journal reported in January Mr Cohen had arranged the payment to Ms Clifford in October 2016 to keep her from publicly discussing the alleged sexual encounter during the presidential campaign.

A week later, In Touch magazine published a 2011 interview with Ms Clifford, in which she claimed she and Mr Trump had a sexual encounter after meeting at a golf tournament in Lake Tahoe, Nevada, a year after Mr Trump’s marriage to his third wife, Melania.

At the end of January, Ms Clifford said in a statement the alleged affair never occurred.

But in a TV interview the same day, she appeared to disown the statement, saying she did not know where it came from and the signature did not look like hers.

-AP