Donald Trump has caused controversy at an event honouring Native American war veterans by referring to a Democratic senator as "Pocahontas".
The remark - described as a "racial slur" by critics - was made during a speech at the White House to celebrate Navajo code talkers who served during World War II.
After describing the war heroes as "incredible" and "very special people", the President quickly went on to disparage Massachusetts senator Elizabeth Warren.
Not naming her directly, he alluded to his long-term Democrat sparring partner by saying: "We have a representative in Congress who they say was here a long time ago. They call her Pocahontas. But you know what, I like you."
In 2012, it came to light that Ms Warren had claimed to be part Native American when she was teaching at the University of Texas and the University of Pennsylvania.
The term "Pocahontas" refers to a North American Indian princess who is fabled to have rescued a colonist from death at the hands of her chief father in Virginia before converting to Christianity and moving to London.
Mr Trump repeatedly used the nickname to refer to Ms Warren during his 2016 presidential campaign.
At the time, his attacks were described by Native American leaders as offensive and distasteful.
The Navajo Nation referred to the President's latest comment as a "cultural insensitivity", but said they had no intention of getting caught up in the "ongoing feud between the senator and President Trump."
Ms Warren told MSNBC: "This was supposed to be an event to honour heroes, people who put it all on the line for our country, who, because of their incredible work, saved the lives of countless Americans and our allies.
"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."
The White House has said the President did not intend to cause any offence.
Press secretary Sarah Huckabee Sanders said it was in fact Ms Warren who was the offensive one when "she lied about something specifically to advance her career".
Mr Trump, who describes himself as "the least racist person that you have ever met", is no stranger to controversial ethnic and racial remarks.
In 2015 he referred to Mexican immigrants as "rapists" - and earlier this year, he sought to ban immigrants from certain Muslim-majority nations.
In the summer, he also attracted criticism for his initial failure to condemn far-right organisations after a woman was killed during clashes in Charlottesville, Virginia.