Speaking at the Conservative Political Action Conference (CPAC), Mr Trump launched an off-script attack on Ms Warren, one of the top Democratic contenders to be the presidential nominee for 2020.
Since the middle of his presidential campaign in 2016, Mr Trump has often called Ms Warren “Pocahontas,” a racial slur which mocks the senator’s claims of Native American ancestry.
“I’m going to regret this. This speech should have been delivered one year from now, not now, damn it.” President Trump said.
“I should have saved the Pocahontas thing for another year because that destroyed her political career and now I won’t get a chance to run against her. I don’t want to knock out all of the good stuff and wind up with somebody who’s actually got talent.”
During the wide-ranging speech, where Mr Trump started by hugging the American flag before walking to the podium to the sound of Lee Greenwood’s “God Bless the USA”, the president went completely off-script.
He let loose against House Democrats, who are broadening their investigations of him, predicted he would win re-election by a greater margin than his 2016 victory, and taunted his potential White House challengers.
Revelling at the adulation he received from CPAC attendees, Mr Trump said: “You know I’m totally off script right now and this is how I got elected, by being off script.
“And if we don’t go off script, our country’s in big trouble, folks, because we have to get it back.”