GOP presidential front-runner Donald TrumpDonald John TrumpBusiness, ballots and battling opioids: Why the Universal Postal Union benefits the US Sanders supporters cry foul over Working Families endorsement of Warren California poll: Biden, Sanders lead Democratic field; Harris takes fifth MORE on Monday called Sen. Elizabeth WarrenElizabeth Ann WarrenSanders supporters cry foul over Working Families endorsement of Warren California poll: Biden, Sanders lead Democratic field; Harris takes fifth Kamala Harris calls for new investigation into Kavanaugh allegations MORE (D-Mass.) an “Indian,” mocking her for an old claim of Native-American ancestry.

Earlier in the day, Warren went on a Twitter rant against Trump, calling him a "loser" and a "serious threat" to the United States.

“You mean the Indian?” Trump asked when a reporter inquired about the senator's comments during a press conference in Washington, D.C. “Who’s that? The Indian?”

ADVERTISEMENT

Trump accused Warren of inflaming tensions between everyday Americans by attacking the legitimacy of his White House run.

“The problem with this country right now is it’s so divided,” he said. "People like Elizabeth Warren really have to get their act together because it’s going to stay divided."

“That includes Hillary,” Trump continued. "And that probably includes me."

Warren met with controversy during her 2012 Senate campaign when reports emerged that Harvard Law School once touted her alleged Cherokee and Delaware ancestors as proof of its faculty’s diversity.