As the director of national intelligence during the Obama administration, James Clapper was involved in handling the Edward Snowden disclosures, winning the release of Americans in North Korea and responding to Russia's efforts to influence the 2016 campaign.

Clapper joined us to discuss President Trump's attacks on the intelligence community, the use of informants and North Korea.

The following is a transcript of the interview with Clapper that aired Sunday, May 27, 2018, on "Face the Nation."

MARGARET BRENNAN: We turn now to the former Director of National Intelligence James Clapper. He advised President Obama for six and a half years, including the period when the Russians were attempting to meddle in the 2016 election. His new book is called Facts and Fears: Hard Truths from a Life in Intelligence. Director Clapper, thank you for being with us--

FORMER DIRECTOR OF NATIONAL INTELLIGENCE JAMES CLAPPER: Thanks, Margaret.

BRENNAN: --this morning. Let's start where we just left off with Senator Rubio. The president is convinced that there was a spy or informant embedded in his campaign and he is asking this question. He tweeted it yesterday. "Why didn't the crooked highest levels of the FBI or Justice contact me to tell me of the phony Russia problem." Can you explain why he says the intelligence community did not inform him of this problem?

CLAPPER: Well, I can't say specifically because this would be a judgment reached by specifically the-the FBI and they may not have felt that the time is appropriate or whether it was-- that there would be any need for it, depending on how this progressed so it's a question of judgment that the FBI would make a tactical judgment to make at the time.

BRENNAN: But as intelligence director you didn't weigh in on a decision of whether or not to inform the campaign?

CLAPPER: No, I did not. I wouldn't have known about informants for lots of reasons. The-- principally the confidentiality of the program and to protect the individual's identity unfortunately which has been exposed, so DNI wouldn't necessarily know about any of FBI's informants nor should that be made known any more than say CIA assets.

BRENNAN: This has now become a talking point for many defenders of the president that he should have been informed. From your point of view, is a generalized briefing just saying be on alert for counterintelligence attempts here enough? Or should the president have specifically or his campaign been specifically warned about this--

CLAPPER: Well again--

BRENNAN: Targeting or risk?

CLAPPER: -- not knowing exactly what the FBI concerns were or what they knew, what the predicate was, it's kind of hard to say. But subsequently certainly particularly when we became more aware of the Russian cyber intrusions both campaigns were-were advised of that.

BRENNAN: Director, you have been critical in your book of the president. He in turn has been very critical of you particularly this week. And I want to play for you a little bit of sound that we have here in a statement he gave to reporters-- I'll read it to you. We don't have it. He said, "There's never been anything like it in the history of our country. If you look at Clapper he sort of admitted that they had spies in the campaign yesterday inadvertently, but I hope it's not true, but it looks like it is." Can you explain what the FBI is intent was here and is the president misunderstanding?

CLAPPER: Well first of all, it is-- I have an aversion to the use of the word spy. But let's just for the sake of discussion use that term which conventionally means the use of tradecraft using a- a formally trained case officer who would mask identity, who would attempt to recruit. So none of the classical attributes of a spy craft if can use that term were present here. This is the most benign form of information gathering. So to characterize it as a spy or spy gate is of course part of the narrative. And it's directly antithetical to what I actually said.

BRENNAN: Well you said in your book one of the more controversial statements that you made in your conclusion is that Russian influence campaign did end up helping to swing the election towards President Trump. What did you conclude that on the basis of? Because you acknowledge it was a very narrow margin of votes that made a difference here.

CLAPPER: Right. First of all, I need to stress Margaret that the intelligence community assessment that we-- the official intelligence the assessment that we rendered and delivered, published on the 6th of January and briefed then president-elect Trump at Trump Tower made no call on whether or not the Russian meddling had any impact on the outcome of the election.

Didn't have the authority or the capabilities or the resources to do that, but as a private citizen having a good understanding of what the Russians actually did and how massive it was and multi-dimensional it was and how many voters it touched and the fact that the election turned on less of 80,000 votes in three states. To me it stretches credulity to think that the Russians didn't have profound impact that could have swung- swung the election. This is not an indictment of anybody who voted for President Trump. It is an indictment of the Russians and the serious threat that they pose and- and their intent to undermine our system.

BRENNAN: But you're saying it's not exactly knowable whether the Clinton loss was a direct result of not campaigning in certain areas?

CLAPPER: No, no. I would not call it an informed opinion.

BRENNAN: Got it. I want to ask you as well about North Korea. You're an old Korea hand, you visited Pyongyang a few years ago. Today we are hearing that U.S. officials have crossed the DMZ to meet with North Koreans to plan this upcoming summit with Kim Jong un. What do they need to nail down to make June 12th worth the president's time?

CLAPPER: Well, I think they should nail down what the outcomes are. What are the intended outcomes for both. And I- I do have some thoughts on this. One, I think it would be a really good thing to establish normalized conduit for communication. That-- and- and I've been an advocate for a long time of having it interest sections established in Pyongyang and Washington at a level below an embassy, but a diplomatic presence nonetheless just as we had in Havana, Cuba for decades to deal with a government we didn't recognize. This is not a reward for bad behavior at all. It's mutually reciprocal and it would give us that presence there, more insight and understanding into North Korea, provide a conduit for information into North Korea and as well give the North Koreans a sense of security by are having an official U.S. presence there.

I also think they should think about just listening to what the North Koreans might say when asked what is it that would take you to feel secure so you don't need nuclear weapons. And one more point we ought to think about: when we say denuclearization of the nuclear-- denuclearization of the Korean peninsula this could have a two way street and that the North Koreans could assert that we have a responsibility to denuclearize and restrict our nuclear umbrella meaning no B-1's, B-2's or B-52's flying into the Korean peninsula-- landing in the Korean peninsula or in operational proximity. So, it seems to me that those are things they ought to discuss. But the main point I would make is why not establish a rig or conduit of communications.

BRENNAN: We will see. Thank you very much Director Clapper.