Washington (AFP) - US First Lady Melania Trump on Friday chose not to leave the White House with her husband as planned to catch a flight to Florida, after a second woman claimed she had an affair with the now president.

The 47-year-old Slovenian-born model skipped the helicopter ride from the White House to Joint Base Andrews, deciding instead to take the longer motorcade on her own to meet Donald for the flight to the Sunshine State for a long holiday weekend.

Reporters traveling with Trump were prevented from seeing the First Lady arrive on the plane, but she did exit the plane at West Palm Beach with Trump.

The pair walked down the stairs together, Melania in dark sunglasses, but she did not smile.

The flight came just hours after former Playboy model Karen McDougal claimed she and Trump had a sexual relationship in 2006, months after Melania Trump gave birth to the president's youngest son Barron.

McDougal also described complex legal and financial agreements that were used in an alleged bid to cover it up.

The White House did not reply to a request for comment. But in a statement to The New Yorker, an unnamed spokesperson said the president had denied having a relationship with McDougal, calling the claims "fake news."

And the first lady's spokeswoman Stephanie Grisham tried to pour cold water on any speculation about the first couple's relationship, saying: ""With her schedule, it was easier to meet him on the plane."

- Deal with a tabloid -

According to The New Yorker, the nine-month relationship between Trump and McDougal ended quietly, but years later -- during the 2016 presidential campaign -- she sold her story.

The New Yorker reported that on August 5, 2016, McDougal agreed to give the company which owns the National Inquirer tabloid exclusive rights over "any romantic, personal, or physical relationship she has ever had with any 'then-married man.'"

The deal is alleged to have been worth $150,000, but the story never ran.

Story continues

"I'm the one who took it, so it's my fault, too. But I didn't understand the full parameters of it," McDougal told The New Yorker of the alleged payment.

The National Enquirer is owned by David Pecker, who has claimed to be a friend of Trump's. The tabloid endorsed Trump's bid for the presidency.

In a statement, the tabloid's owner, AMI, said that the suggestion that it "engages in any practice that would allow it to hold influence over the President of the United States is laughable."

The model's story strongly echoes allegations of an affair between Trump and the porn star Stephanie Clifford -- known as Stormy Daniels -- during the same period.

In that case, the president's personal lawyer Michael Cohen admitted to paying Daniels $130,000 but refused to say why.

After that admission, Daniels' agent has said she feels free to speak out.

"Everything is off now, and Stormy is going to tell her story," manager Gina Rodriguez told US media.

- 'Lawful' payment to porn star -

Good governance groups believe that Cohen's payment could constitute a campaign donation and breach election financial rules.

Cohen has refused to say why he paid Daniels the vast sum but he claims he was not reimbursed by the "Trump Organization nor the Trump campaign."

"The payment to Ms Clifford was lawful, and was not a campaign contribution or a campaign expenditure by anyone," Cohen said.

Trump declined to comment on the issue. The White House has dodged questions about whether allegations of an affair are true, claiming the matter was dealt with during the campaign.

Last month, celebrity magazine In Touch published a 2011 interview with Daniels in which she details having "textbook generic" sex with Trump.

She recalled meeting Trump at a celebrity golf tournament in 2006, shortly after Melania gave birth to Barron.