President Donald Trump, right, meets with Navajo Code Talkers Peter MacDonald, centre, and Thomas Begay, left, in the Oval Office of the White House in Washington. Picture: Susan Walsh/AP

Washington - President Donald Trump said there was a "Pocahontas" in the US Congress during a meeting on Monday with Native American World War Two veterans in an apparent derogatory reference to Democratic Senator Elizabeth Warren of Massachusetts.

After listening to one veteran speak at length about his experience as a "Navajo code talker" during the war, Trump heaped praise on the veterans and said he would not give prepared remarks himself.

"You were here long before any of us were here," Trump said. "Although we have a representative in Congress who they say was here a long time ago. They call her Pocahontas."

Trump repeatedly referred to Warren as "Pocahontas," the name of a famous 17th-century Native American, during his presidential campaign in a mocking reference to Warren's having said in the past that she had Native American ancestry.

Warren, one of the Senate's most prominent liberal Democrats, is a noted legal scholar who taught at Harvard Law School and served as an adviser to former President Barack Obama before she was elected to the Senate in 2012.

"It is deeply unfortunate that the president of the United States cannot even make it through a ceremony honouring these heroes without having to throw out a racial slur," Warren said on MSNBC.

White House spokesperson Sarah Sanders disputed the characterisation of Trump's remark as a racial slur.

"I think what most people find offensive is Senator Warren lying about her heritage to advance her career," Sanders told reporters.

Jefferson Keel, president of the National Congress of American Indians, questioned the "use of the name Pocahontas as a slur ... Once again, we call upon the president to refrain from using her name in a way that denigrates her legacy.”

Trump's comment immediately trended on social media. The word "Pocahontas" appeared 12 times on Twitter every second, according to social media analytics company Zoomph.

Trump's knock at Warren came as his administration is embroiled in controversy over the Consumer Financial Protection Board, which Warren helped develop before entering politics.

The agency, set up to protect Americans from abusive lending practices after the financial crisis, has been under attack by Trump since he took office in January.

On Friday, Trump named his budget director as the interim head of the agency, after its outgoing chief named someone else to the job, setting up a court battle.