WASHINGTON — Escalating the fight with his own liberal base, President Obama, in an interview posted online on Saturday, took on Senator Elizabeth Warren, a champion of the left, by suggesting that she was motivated by politics in her battle against his proposed Pacific trade accord.

Mr. Obama said that some of Ms. Warren’s warnings about the potential damage of the trade deal were nothing more than the “hypotheticals” of a law-school professor and, repeating an assertion he used recently, “absolutely wrong.”

“The truth of the matter is that Elizabeth is, you know, a politician like everybody else,” Mr. Obama told Matt Bai of Yahoo News in an interview conducted on Friday at Nike’s headquarters near Beaverton, Ore. “And, you know, she’s got a voice that she wants to get out there, and I understand that. And on most issues, she and I deeply agree. On this one, though, her arguments don’t stand the test of fact and scrutiny.”