President Donald Trump said that if Massachusetts Democratic Sen. Elizabeth Warren is in a 2020 presidential debate against him, he will -- at that time -- offer $1 million to her favorite charity on the spot if she takes a DNA test to prove her Native American heritage.

Warren, who originally is from Oklahoma, has maintained that her mother's family has Cherokee or Delaware ancestry.

Trump said his critics have pressured him to apologize to Warren for the "Pocahontas" moniker.

However, Trump said at the Great Falls, Mont. rally that he apologizes to the original Pocahontas -- a 17th Century Native American woman who married English settler John Rolfe and later moved with him to near present-day Henrico County, Va.

Trump said that when or if Warren "proclaims she's of Indian heritage" he will order a DNA test kit from one of the television commercials he views.

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At the prospective debate, he will "gently" toss the kit in Warren's direction and "say I will give you a million dollars to your favorite charity -- paid for by Trump -- if it show's you're an Indian."

One of Warren's senatorial opponents, Independent candidate Shiva Ayyadurai, previously shipped a kit to Warren, which he said was refused.

Trump said Warren and former Vice President Joe Biden are likely to announce bids to face him in 2020.

Trump was in Great Falls to stump for State Auditor Matt Rosendale (R), who is facing Sen. Jon Tester (D-Mont.) this fall.

UPDATE: Sen. Warren fired back on Twitter:

'Pocahontas' Controversy: New England Native American Leader Calls Warren's Claims 'Insult'