Donald Trump’s proposal to use a “deportation force” to deport millions of undocumented immigrants is unrealistic, President Obama said in an exclusive interview today with ABC News’ Chief Anchor George Stephanopoulos.

“The notion that we’re gonna deport 11, 12 million people from this country — first of all, I have no idea where Mr. Trump thinks the money’s gonna come from. It would cost us hundreds of billions of dollars to execute that,” the president told Stephanopoulos in an interview at the White House.

“Imagine the images on the screen flashed around the world as we were dragging parents away from their children, and putting them in what, detention centers, and then systematically sending them out,” the president said. “Nobody thinks that that is realistic. But more importantly, that’s not who we are as Americans.”