President Obama criticized Republican presidential contender Donald Trump's latest immigration proposal on Thursday, saying the real estate mogul's plan to use a "deportation force" to send millions of illegal immigrant home is unrealistic and would cost too much.

"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," Obama said in an interview with ABC News' George Stephanopoulos. "It would cost us hundreds of billions of dollars to execute that."

Trump has made immigration a central plank of his presidential campaign and insists that the U.S. can successfully and humanely deport the estimated 11 million immigrants living in the country illegally. On Wednesday, he doubled down on those claims by saying he would build a massive deportation force to carry out his immigration proposal, reported CNN.

"Nobody thinks that's realistic," Obama said of Trump's plan. "That's not who we are as Americans."

Obama added: "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 he thinks some Americans support Trump's immigration ideas because there has always been a strain of anti-immigrant sentiment in the U.S., which Obama said is ironic considering many of those people's ancestors were immigrants only one or two generations ago.

"It's the job of leaders not to play into that sentiment," he added. "We don't want, I think, a president or any person in a position of leadership to play on those kinds of fears."

But Trump continued to push his plan on Thursday, telling Fox News' Bret Baier that it's not "mean-spirited," but rather a "business" decision that would be logistically possible "if it's managed properly," reported the Washington Examiner.

"It's basically quite simple, but it's going to be done in a very humane fashion. People will have to go out. They are illegal immigrants. They came in illegally. They have to go out, and they have to come back legally. There will be a deportation, and hopefully they'll be able to come back into the country," Trump said.

"We have a country - you don't have a country if people are allowed to walk in, cross the border and stay here as long as they want," he added. "You don't have a country, and everybody knows it. Everybody knows I'm right. I'm saying this: It will be done in a humane way. It'll be done professionally."