Former CIA chief unsure Trump 'has done the homework needed' on North Korea “Kim Jong Un knows his program inside and out,” former CIA Director Hayden said.

Former CIA Director Michael Hayden said he is unsure President Trump has “done the homework needed” for negotiations with North Korea over its nuclear program.

“Kim Jong Un knows his [nuclear] program inside and out,” Hayden told ABC News Global Correspondent and “This Week” co-anchor Martha Raddatz on Sunday. “I think he knows what he can concede and what it means and what he cannot concede.”

“I don't know that the president has done the kind of homework" to give him the same level of knowledge, said Hayden, who headed the CIA under Presidents George W. Bush and Obama, and who also served as director of the National Security Agency under both Bush and President Clinton.

Hayden said he hopes any summit between Trump and North Korean leader Kim Jong Un "stays at the level of principles," rather than delving into specifics.

Hayden said that, ideally, in the summit, “They talk about denuclearization, allow each side to kind of cower within the ambiguity of denuclearization, and then, seriously begin a process that makes the peninsula less dangerous than it is today.”

The former intelligence official also discussed his concern that demanding that North Korea entirely give up its nuclear program could end "in a very bad place."

Hayden said he agrees with Republican Sen. Marco Rubio, who said during an earlier appearance on "This Week" Sunday that Kim Jong Un is not going to denuclearize.

"I totally agree with Sen. Rubio," Hayden said. "These folks are not going to get rid of all their nuclear weapons. And if President Trump's 'brand,' and that's the right word here, going into this meeting demands something like that, this is going to end up in a very bad place."

Raddatz asked whether Trump and Kim might characterize the outcome an eventual summit differently with, for example, Trump's saying he accomplished "denuclearization" of the Korean Peninsula, and Kim's referring simply to "arms control."

Hayden said that would be a positive result.

"I hope that's where we come out," he said. "I think that's the most optimistic scenario. You have the meeting. Everyone smiles. Everyone shakes hands. And everyone agrees on a work program that they give to their staffs that moves the Korean Peninsula in a direction of being more stable, more transparent, less prone to war. But I don't think we're going to have a parade of missiles or weapons going through some destruction site that we can put on camera."

Hayden, who just released a book titled, “The Assault on Intelligence: American National Security in an Age of Lies,” also commented on recent claims by the president that the FBI spied on his presidential campaign.

“I think [President Trump] is simply trying to delegitimize the Mueller investigation, the FBI, the Department of Justice, and he’s willing to throw almost anything against the wall" to see if it sticks, Hayden said.