Washington Republican US presidential candidate Donald Trump has threatened to bring Gennifer Flowers, who once had an affair with former president Bill Clinton, to a debate with Hillary Clinton.

Trump made the threat after fellow businessman Mark Cuban, a vocal Trump opponent and Clinton supporter, said he would be in the front row for the debate.

"If dopey Mark Cuban of failed Benefactor fame wants to sit in the front row, perhaps I will put Gennifer Flowers right alongside of him!" Trump wrote on Twitter.

Flowers revealed an affair with Bill Clinton during his 1992 presidential campaign. He initially denied the relationship, but later admitted the sexual relationship under oath.


Flowers responded on her own Twitter account: "Hi Donald. You know I'm in your corner and will definitely be at the debate!"

Clinton and Trump are to face off in the first of three televised presidential debates on Tuesday.

Speaking in Roanoke, Virginia, Trump told supporters that Clinton likes to say she's been fighting for women and children for decades. He then asked why 70 million women and children are in poverty or on the brink of poverty.

Clinton co-founded the Arkansas Advocates for Children & Families early in her career and delivered a seminal speech as first lady declaring that "women's rights are human rights."

Trump has been criticised for crass comments he's made about women over the years.