A Democratic senator has challenged Donald Trump to make good on a pledge to donate $1 million to charity if a DNA test proved she has Native American ancestry.
Ms Warren sent a tweet reminding Mr Trump of his offer to give $1 million to a charity of her choice. "Remember saying on 7/5 that you’d give $1M to a charity of my choice if my DNA showed Native American ancestry?"
She added: "I remember – and here's the verdict. Please send the check to the National Indigenous Women’s Resource Center".
Known as a liberal firebrand in her party, Ms Warren is a former Harvard Law School professor who has championed populist economics including student loan reform and a higher minimum wage.
Having some memory problems, @realDonaldTrump? Should we call for a doctor?
Here’s something you won’t “forget,” Mr. President: You’re the least popular president in modern history & your allies will go down hard in the midterm elections. 22 days. Tick-tock, tick-tock. pic.twitter.com/53FV0HXGXX
— Elizabeth Warren (@elizabethforma) October 15, 2018
The US president has repeatedly called Ms Warren "Pocahontas," the name of a 17th century Native American chief's daughter, to draw attention to a controversy over her heritage raised during her 2012 Senate race.
When Mr Trump was asked about the DNA test on Monday, he said, "Who cares?" as he left Washington to visit hurricane-stricken areas in Florida and Georgia.
"I hope she's running for president, because I think she'll be very easy," he added.
Asked whether he would pay $1 million to charity, Mr Trump told reporters: "I didn't say that. I didn't - you better read it again."
Taunting her over her claims in July, Trump said: "I will give you a million dollars to your favorite charity, paid for by Trump, if you take the test and it shows you're an Indian.
"I have a feeling she will say no," he said.
Ms Warren provided the DNA test results in a statement on her campaign website, suggesting she has a Native American ancestor dating back six to 10 generations.
The report was carried out by Stanford University professor Carlos Bustamante. It states that "the vast majority" of Ms Warren's ancestry is European but the results "strongly support the existence " of a Native American ancestor.
The DNA test is the latest sign that Ms Warren intends to put her name forward for the Democratic presidential nomination in 2020.
The Democrat has denied benefiting from her background since she ran for the Senate in 2012, when it emerged that she was listed as a minority in a Harvard Law School directory.
She has frequently faced attacks from the White House and Republicans who have suggested she used claims of native ancestry to advance her academic career.
Along with her DNA results, Ms Warren released a web page featuring documents, videos and written testimonies from colleagues and employers at Harvard stating her background did not feature in their hiring decisions.
Among them is one from Republican President Ronald Reagan's former solicitor general, Charles Fried, who wrote: "I recommended Elizabeth Warren to the faculty of Harvard Law School because she is a tremendous teacher...She is an important scholar."
He added of her ancestry: "I knew nothing about this at the time I studied her credentials... It never came up."
Ms Warren, who is a senator for Massachusetts, has said she will take a "hard look" at challenging Mr Trump in 2020 after November's midterm elections.
However the senator has been involved in election races in all 50 states and studiously called every candidate who has won their local Democratic primary.
She has also deployed staff to the four states - New Hampshire, Iowa, South Carolina and Nevada = where early presidential primaries take place.
"If you were advising someone who had the resources of someone who was going to run for president, this is what you would do," David Axelrod, President Barack Obama's former adviser, told the Washington Post.