Reverting to his campaigning days, President Trump offered some red meat to his base during an appearance at a campaign rally in Montana on Thursday when he joked about offering Massachusetts Senator Elizabeth Warren $1 million to take a genetics test that would prove (or disprove) her native American heritage.

Trump lobbed insults at "Pocahontas", adding that he wouldn't apologize for using what some believe to be a racially charged nickname.

Claiming that Warren has "based her life" around "being a minority," Trump said that if Warren wins the Democratic nomination in 2020, he would offer her $1 million to take a DNA test to conclusively prove that she does have Native American heritage.

"But let’s say I’m debating Pocahontas, I’ll do this," Trump said during a rally in Great Falls, Mont. "Pocahontas, they always want me to apologize for saying it. You know those little kits you see on television for $2 - learn your heritage - we will very carefully take that kit, since we're in the #MeToo generation, we've got to be very gentle, we will gently take that kit and we will slowly toss it, hoping it doesn't hit her and injure her arm, even though it only weighs probably 2 oz.," Trump said. "And we will say, 'I will give you a million dollars, paid for by Trump, to your favorite charity if you take the test and it shows you’re an Indian," Trump said. "And we’ll see what she does. I have a feeling she will say no but we will hold it for the debates."

Trump often attacks Warren at his rallies, like he did at a rally in Nevada last month. However, he once again refused to apologize for using the nickname, which some have derided as racist.

"Pocahontas, I apologize to you," Trump said Thursday. "To the fake Pocahontas, I won’t."

Afterward, Warren fired back at Trump on twitter, accusing him of obsessing over Warren's "genes" while his administration carries out "DNA tests on little kids because you ripped them from their mamas & you are too incompetent to reunite them in accordance with a court order."

Hey, @realDonaldTrump: While you obsess over my genes, your Admin is conducting DNA tests on little kids because you ripped them from their mamas & you are too incompetent to reunite them in time to meet a court order. Maybe you should focus on fixing the lives you're destroying. — Elizabeth Warren (@elizabethforma) July 5, 2018

"Maybe you should focus on fixing the lives you're destroying," she added.

Warren has defended her claims of Native American heritage, saying she's never "used it for anything" or benefited from it in any way.