WASHINGTON • US President Donald Trump said on Thursday he had heard Democratic vice-presidential running mate Kamala Harris was not eligible to serve, stoking a false claim echoing the baseless "birther" theory he promoted about former president Barack Obama.

Mr Trump was asked about "claims circulating on social media" that Ms Harris was not eligible and whether she met the legal requirements for vice-president.

"I heard it today that she doesn't meet the requirements. And, by the way, the lawyer that wrote that piece is a very highly qualified, very talented lawyer. I have no idea if that's right," Mr Trump said.

"I would have assumed the Democrats would have checked that out before she gets chosen to run for vice-president.

"But that's a very serious - you're saying that - they're saying that she doesn't qualify because she wasn't born in this country."

The reporter replied that Ms Harris was born in the US but her parents might not have been permanent residents at the time.

Mr Trump appeared to be referring to a Newsweek op-ed that wrongly claimed Ms Harris was not eligible to serve as vice-president because of her parents' immigration status when she was born.

Ms Harris was born in Oakland, California, in 1964, to a father from Jamaica and a mother, from India.

Mr Trump earned national political prominence by promoting the "birther" lie that Mr Obama, the US' first black president, was not born in the US. He grudgingly acknowledged late in his 2016 presidential campaign that Mr Obama was born in the United States.

In his Newsweek op-ed, Chapman University law professor John Eastman claimed some "commentators" said Ms Harris was ineligible as she was not a "natural-born citizen" as her parents were not naturalised US citizens at the time of birth.

According to the Constitution, any natural-born US citizen over the age of 35 is eligible to be president or vice-president.

Constitutional law expert Erwin Chemerinsky said the claim "is a truly silly argument".

"Under Section 1 of the 14th Amendment, anyone born in the United States is a United States citizen. The Supreme Court has held this since the 1890s," he said.

Harvard Law School professor of constitutional law Laurence H. Tribe said Prof Eastman's idea was "total BS".

"I hadn't wanted to comment on this because it's such an idiotic theory," Prof Tribe told the paper.

AGENCE FRANCE-PRESSE