The President also used the Thursday meeting at the White House to again surface unfounded claims of voter fraud during the 2016 presidential election.
The sources said the Warren moment came up in the context of Trump's impromptu analysis of the state of the Democratic Party. Trump made his comments in what appeared to be a reference to Warren's criticism of Attorney General Jeff Sessions during his confirmation process. Her comments prompted Republicans to invoke an arcane rule to cut her off.
The moment galvanized Democrats and has elevated Warren's standing among progressives.
Trump used his pejorative campaign nickname for Warren -- a reference to her claims of having Native American ancestry -- several times during the meeting, which one source described as "equal parts bizarre and completely awkward."
At one point, Trump said the only reason Warren claimed Native American heritage was "because she has high cheekbones," one of the sources said.
The White House and Warren's office haven't responded to a CNN request for comment. The story was first reported by Politico
For Trump, it was a unscheduled -- and unsolicited -- return to a frequent campaign riff attacking Warren, who at the time served as a top surrogate to Democratic nominee Hillary Clinton. In doing so, he was digging back into questions over Warren's ancestry from her 2012 Senate race, which Warren defended at the time, in part, by citing the high cheekbones of her grandfather.
"She's got less Native American blood in her than I have, OK?" Trump said during a July rally in North Carolina. "Believe me ... She goes, 'Well look at my cheekbones.'"
Trump, in a similar line of attack during a Washington state rally in May, called Warren "a total phony."
While it became a campaign trail staple, it was, according to one of the sources, the first time anyone in the room had heard it in full.
"It's not like we were on the trail with him," the source said. "And a closed-door meeting with senators at the White House is about the furthest thing from a campaign rally."
Three sources familiar with the meeting also said Trump spoke about his baseless voter fraud claims at the same meeting.
The sources said Trump complained about thousands of people being bused from Massachusetts to vote illegally in New Hampshire, a state he narrowly lost. The comments were prompted by the presence of former Sen. Kelly Ayotte, a New Hampshire Republican, who attended the meeting because of the role she is playing helping Judge Neil Gorsuch win confirmation to the Supreme Court, something he thanked her for in the meeting.
In a teasing and lighthearted way, Trump said to Ayotte, "I wish you had endorsed me like you endorsed him," referring to Gorsuch and Ayotte's distancing of herself from Trump late in his controversial campaign.