WASHINGTON (AP) — Sen. Elizabeth Warren labeled Donald Trump a loser, a bully and a threat on Monday, continuing a fierce war of words between the liberal icon and the front-running Republican presidential candidate that has played out on social media and The New York Times.

"@RealDonaldTrump knows he's a loser. His insecurities are on parade: petty bullying, attacks on women, cheap racism, flagrant narcissism," the Massachusetts Democrat wrote on her campaign's Twitter account on Monday, part of a rapid-fire burst of eight tweets attacking the billionaire television personality.

"But just because @realDonaldTrump is a loser everywhere else doesn't mean he'll lose this election," Warren warned her allies.

A week ago, Warren took to Facebook to try stirring up Trump opponents to speak out.

"Donald Trump is a bigger, uglier threat every day that goes by — and it's time for decent people everywhere — Republican, Democrat, Independent — to say No More Donald," she wrote.

Trump poked back in an interview with New York Times writer Maureen Dowd in a column that appeared in Sunday's newspaper.

Trump said of Warren's criticism: "I think it's wonderful because the Indians can now partake in the future of the country. She's got about as much Indian blood as I have."

"Her whole life was based on a fraud," he added. "She got into Harvard and all that because she said she was a minority."

During her 2012 election campaign, Warren was criticized after being listed in law school directories as having Native American ancestry.

At a press conference in Washington Monday, Trump was mostly dismissive when asked about Warren's comments.

"The problem with the country right now, it's so divided," he said. "And people like Elizabeth Warren really have to get their act together."

The exchange comes with Trump leading the race for convention delegates over two surviving competitors and some GOP leaders trying to head off his nomination, saying he would be defeated and cause losses for GOP congressional candidates.

In her tweets, Warren accused Trump of running failed businesses, cheating people and using bankruptcies to avoid debts.

She said he was "ready to tear apart an America that was built on values like decency, community, and concern for our neighbors." And she wrote, "Many of history's worst authoritarians started out as losers — and @realDonaldTrump is a serious threat."

"The way I see it, it's our job to make sure @realDonaldTrump ends this campaign every bit the loser that he started it," Warren tweeted Monday on her campaign account, which has 261,000 followers.

Trump, a prodigious tweeter, has 7 million followers on his account.

Warren has yet to issue an endorsement in the Democratic presidential contest between former Secretary of State Hillary Clinton and Sen. Bernie Sanders, I-Vt.

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Associated Press writer Jill Colvin reported from Washington.