US Democratic Senator Elizabeth Warren is facing a backlash after revealing a DNA test, which she says validates her claims of Native American heritage.
The Cherokee Nation slammed the results for showing trace amounts of native DNA. US President Donald Trump later took to Twitter to taunt Ms Warren.
Many analysts speculate that Ms Warren, whose heritage Mr Trump has often mocked, is running for president.
Ms Warren has not claimed to be a citizen of any US tribal nation.
"Even they don't want her," Mr Trump said on Tuesday in response to the statement by the Cherokee Nation, the largest tribal nation in the US.
"Thank you to the Cherokee Nation for revealing that Elizabeth Warren, sometimes referred to as Pocahontas, is a complete and total Fraud!" he wrote on Twitter, referencing the daughter of the 17th-Century indigenous chief.
Cherokee Nation Secretary of State Chuck Hoskin Jr said in a statement on Monday that "a DNA test is useless to determine tribal citizenship".
Pocahontas (the bad version), sometimes referred to as Elizabeth Warren, is getting slammed. She took a bogus DNA test and it showed that she may be 1/1024, far less than the average American. Now Cherokee Nation denies her, “DNA test is useless.” Even they don’t want her. Phony!— Donald J. Trump (@realDonaldTrump) October 16, 2018
Now that her claims of being of Indian heritage have turned out to be a scam and a lie, Elizabeth Warren should apologize for perpetrating this fraud against the American Public. Harvard called her “a person of color” (amazing con), and would not have taken her otherwise!— Donald J. Trump (@realDonaldTrump) October 16, 2018
"Using a DNA test to lay claim to any connection to the Cherokee Nation or any tribal nation, even vaguely, is inappropriate and wrong," Mr Hoskin said, adding that current tests do not differentiate between peoples from the North and South American continents.
Mrs Warren later tweeted: "DNA & family history has nothing to do with tribal affiliation or citizenship, which is determined only - only - by Tribal Nations".
"I respect the distinction, & don't list myself as Native in the Senate."
Trump's battle cry
Analysis by Anthony Zurcher, BBC Washington
Elizabeth Warren's efforts to put to rest the story of her native American ancestry is a case study in the difficulty of engaging Donald Trump on his terms.
He challenged her to take a DNA test, which she did. While the results supported her account, they were by no means definitive. The president pounced, pointing to the lowest-end estimation of her native American DNA and labelling her a phony, calling her story a fraud and a scam.
Complicating the matter for Ms Warren is that the tribal identity is a sensitive matter for native Americans. The Cherokee nation pushed back hard on the notion that anyone could claim membership based on a DNA test (even though Ms Warren had made no such attempt).
Ms Warren also offered accounts from colleagues supporting her contention that she received no benefits or preference for her past claims, but the furore over the DNA debate buried those efforts.
So rather than end the conversation, Ms Warren has effectively given her critics further ammunition to use against her. The president is sticking with his derisive "Pocahontas" nickname - and, if anything, he may more strongly believe this is a political weakness he can exploit.
What did the test find?
The Massachusetts progressive senator's DNA report was conducted by geneticist Carlos Bustamante of Stanford.
"The vast majority" of Ms Warren's ancestry is European, it concludes, but "the results strongly support" a Native American ancestor.
This puts Ms Warren as between 1/64 and 1/1,024 Native-American, according to the Boston Globe.
In a campaign-style video revealing her DNA test results on Monday, Ms Warren says her critics attack her as an insult or "to distract from the kinds of changes I'm fighting for".
Analysts in Washington immediately regarded the video as evidence that she is considering a presidential run in 2020.
How has Warren been taunted?
Ms Warren has denied benefiting from her background since 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 over whether she used claims of native ancestry to advance her career.
At a rally in July, the US president said he would give $1m (£761,000) to charity if Ms Warren would prove her claims of Native-American heritage.
On Monday, Mr Trump was asked about the charity pledge and initially denied that he had ever made it.
But later while touring hurricane damage in Florida, he said he would only give money "if I can test her personally".
"That will not be something I will enjoy," he added.
Mrs Warren later took to Twitter to call Mr Trump's remark a "creepy physical threat", and called for the donation to be made to the National Indigenous Women's Resource Center.
What have others said?
South Carolina Republican Senator Lindsey Graham told Fox News on Tuesday that he also intends to take a DNA test to see if he can "beat" Ms Warren's results.
"I've been told that my grandmother was part Cherokee Indian. It may all be just talk, but you're gonna find out in a couple of weeks," he said.
Cherokee writer and genealogy researcher Twila Barnes said on her blog that "Warren has done more harm with this DNA test than she ever did with her false claim of being Cherokee".
She called the DNA test "a political attack on tribal sovereignty".
University of Alberta professor and author Kim Tallbear said that Ms Warren is using a "settler-colonial definition of who is Indigenous".
"She and much of the US American public privilege the voices of (mostly white) genome scientists and implicitly cede to them the power to define Indigenous identity.
"As scholars of race have shown, it is one of the privilege of whiteness to define and control everyone else's identity," she wrote.
However, Deb Haaland, a Native American woman running for Congress in New Mexico, welcomed Ms Warren's genetic test, saying it "confirms the family history she has long shared with the world, and I acknowledge her Native ancestry as testament to who we are as Americans".
"The revelation of Senator Warren's Native American ancestry is significant for her personally, and I join her in celebrating her ancestry," tweeted Ms Haaland, a member of the Pueblo of Laguna Tribe.
Senator Warren has been a sister in the struggle for years for Indigenous peoples' rights, and for all of us who weren't born into the top 1%. The revelation of Senator Warren’s Native American ancestry is significant for her personally, and I join her in celebrating her ancestry— Deb Haaland (@Deb4CongressNM) October 15, 2018
How does this echo Trump attacks on Obama?
The hubbub around Ms Warren's ancestry recalls the attacks President Barack Obama faced over his background.
During Mr Obama's campaign, Mr Trump called repeatedly for him to release his birth certificate to prove he was born in America.
The rumours that Mr Obama was a foreigner persisted throughout his presidency and, in 2011, the White House released his birth certificate to quash the controversy.