US President Donald Trump is reportedly continuing to refer to Senator Elizabeth Warren as 'Pocahontas', a nickname he used for her during his election campaign.

Warren, a Democrat senator from Massachusetts, has a well-documented feud with the Republican, with the pair frequently taking to Twitter to exchange barbs.

Trump took to referring to Warren as 'Pocahontas' in a reference to her Native American ancestry, which he has claimed is fabricated, while she insists is her background.

During a meeting on 10 February, Trump had referred to Warren as Pocahontas several times, while discussing her opposition to Trump's Attorney General pick Jeff Sessions, who was confirmed this week, largely refusing to use her real name.

He reportedly told Democrats: "Pocahontas is now the face of your party," New York Daily News reported.

On his campaign trail, Trump told NBC correspondent Hallie Jackson: "We call her Pocahontas for a reason. She said she's 5% Native American. She was unable to prove it.

"She used the fact that she was Native American to advance her career. Elizabeth Warren is a total fraud. I know it. Other people who work with her know it. Elizabeth Warren is a total fraud."

Trump added: "She made up her heritage, which I think is racist. I think she's a racist, actually, because what she did was very racist."

In response, Warren referred to Trump as a "thin-skinned bully" and said he was not fit to be president.

"Fling as much mud as you want, @realDonaldTrump. Your words & actions disqualify you from being President – & I won't stop saying it," she tweeted.