Former Secretary of Defense Robert Gates criticized Donald Trump's foreign policy Sunday on ABC's This Week, days after Trump gave a speech detailing his views on foreign policy in Washington, DC.

When host Martha Raddatz asked Gates what a Trump presidency would mean for American national security, Gates said that Trump "doesn't understand the difference between a business negotiation and a negotiation with sovereign powers."

"He doesn't understand that there's a give and take in international relations that is different than in the business community. And just one further comment: He talks about walking," Gates said. "How do you walk away from China, a country that holds a trillion dollars in US treasuries and with which we have a half a trillion dollars in trade every year and at the same time say we're gonna launch a trade war against them at the same time we're asking them to pressure North Korea."

Gates said that Trump's policies appear unrealistic or do not include details.

"For example, he, on the one hand says we need to be a more reliable ally to our friends and in the next breath he basically says we're gonna rip up all those burden-sharing agreements that we've had over the decades with them and make them go their own way if they don't pay for everything," Gates said. "He says some things that it's hard to disagree with. The allies ought to be doing more. But how do you get them there when you're dealing with 28 sovereign countries and, you know, nobody argued harder for them to do more than I did."

Gates said that Trump does not listen, a problem that past presidents the former defense secretary worked with did not have.

"One of the things that worries me, Martha, is that he doesn't listen to people. He believes that he has all the answers, that he's the smartest man in the room. … I've worked for some very different presidents, Jimmy Carter and Ronald Reagan, George W. Bush and Barack Obama, one of the things they all had in common was a willingness to listen to people who had experience and then make their own independent judgments," Gates said."Now they've gone in different directions, but they never assumed that they had all the answers and that's one of the things that troubles me."