The following is a transcript of the interview with former Secretary of State John Kerry that aired Sunday, Sept. 2, 2018, on "Face the Nation."

FMR. SECRETARY KERRY: You work to implement our democracy by reaching out across the aisle, by building relationships, by believing in the better angels of American value system. And I think John McCain did that. I did that, others have done that. But right now we have a culture divide that has been accentuated by political so-called leaders. And what they're doing is they're operating in a fact-less world. And my book, I think, is a- a display of the ways in which you challenge those who would try to tear it apart and not deal with facts and how you in fact can hold the system accountable and get back- back to the fact-based democracy we rely on.

MARGARET BRENNAN: Are you going to be hitting the campaign trail?

FMR. SECRETARY KERRY: You bet I am. -I think that's the most important work we can do right now is trying to elect people on a national basis and--

MARGARET BRENNAN: Well-

SEC. KERRY -- and restore the leadership that the country needs.

MARGARET BRENNAN: --How do you define what Democrats stand for these days?

FMR. SECRETARY KERRY: I- I think each Democratic candidate is going to define it as they go out and speak to people in their districts, and out of that I believe will come the future consensus that's necessary to take a party as a whole to a better place.

MARGARET BRENNAN: But it's a party in crisis.

FMR. SECRETARY KERRY: Well- I'll probably get smacked for this but, you know, what I learned running for president is that you don't have a party per se where you have adherence to a strict platform et cetera. You have an amalgamation. You have a group of people who call themselves democrats, but they speak with different nuances and different approaches to various aspects of political choices- life.

MARGARET BRENNAN: Are you going to run in 2020?

FMR. SECRETARY KERRY: I'm really not thinking about it. Talking about 2020 right now is a total distraction and waste of time. What we need to do is focus on 2018.

MARGARET BRENNAN: Well I'm going ask you that same question sometime after November.

FMR. SECRETARY KERRY: If you catch me.

MARGARET BRENNAN: --If I catch you. You mentioned running- in 2004 and you write a lot about it and some detail you hadn't actually made public before, some of the difficulties along the way.

FMR. SECRETARY KERRY: Yeah. There's a lot of-I've never said anything much about it.

MARGARET BRENNAN: You made the decision not to challenge that election in Ohio. You came up 118,000 votes short.

FMR. SECRETARY KERRY: I thought the better thing to do was to move on, to concede, to- to keep America from having to go through a lawsuit over its election at a time that we were at war and when there were very clear realities about where it was going to wind up in that kind of a lawsuit. We would've lost because we would have had the exact same outcome that Al Gore had four years earlier. I didn't want to waste the country's time or my time in what I think would have been completely taken as a personal and venal effort by me to, you know, take care of myself not take care of the country.

MARGARET BRENNAN: Do you regret not fighting back harder against the Swift Boat attack ads?

FMR. SECRETARY KERRY: I do regret that- and I say this in the book. I'm very clear, and I take responsibility for it. It is my- it's my ultimate decision. I'm responsible for it not having happened. But yes I believe it was vital, particularly in the last days of the campaign, to be addressing advertisements that were such a grotesque distortion of the reality of what happened in the rivers of Vietnam.

MARGARET BRENNAN: And you regret picking John Edwards as your vice presidential candidate?

FMR. SECRETARY KERRY: I write in the book about the qualities that you are looking for when you choose a vice president and I think when you articulate those qualities and then you measure what took place against the qualities that I very much lay out there that you're looking for, it- it didn't measure up. It wasn't what we had hoped for. So there was some disappointment in that.

MARGARET BRENNAN: I want to ask you about another key relationship: Barack Obama. Specifically you said, "I never succeeded in persuading him to give me the tool I wanted most: greater leverage."

FMR. SECRETARY KERRY: Correct.

MARGARET BRENNAN: What do you mean?

FMR. SECRETARY KERRY: Well from the moment I was nominated and asked, "What about Syria?" I said we have to change Assad's calculation. And throughout the four years I was secretary of state, privileged to be so, I always raised the issue in the meetings we had about how we needed to change that calculation. I particularly believed that after Assad had been violating ceasefires. It was clear he needed to be taught a lesson. He needed to know that we were going to hold him accountable. And I raised that directly with the Russians, and I put several ideas on the table. The president was not persuaded by my argument. I believed that we had several options we could have done at very low risk to be able to make it clear to Assad that when we had a cease fire and when he said he was going to live by it he had to live by it. And I thought we should have done that. And as I--

MARGARET BRENNAN: Was he too risk averse?

FMR. SECRETARY KERRY: As I say in the book, my job and the job of anybody in a cabinet is to put an idea in front of the president, to argue the idea. The president is the decider. And there is no clarity by which I can say to you I was 100 percent right or the president was 100 percent wrong or vice versa. Those are the judgments that are made by a president.

MARGARET BRENNAN: But do you think he was too risk averse?

FMR. SECRETARY KERRY: No I think he had an attitude about Syria and a judgment about Syria. And he had a feeling about where that might take him if he made some of the decisions that I and others proffered.

MARGARET BRENNAN: Well you write about this in detail. It's an entire chapter in the book because you, to be very frank, were hung out to dry here because you went on television--

FMR. SECRETARY KERRY: I don't write that. I don't say I was hung out to dry and you know that.

MARGARET BRENNAN: --No that's my characterization. I know that. I don't say that's my characterization-

FMR. SECRETARY KERRY: You're characterizing my-

MARGARET BRENNAN: --I'm characterizing your retelling though, where you went out and you made this--

SEC KERRY: What I write about is the degree-

MARGARET BRENNAN: --prosecutorial, very careful argument about the chemical weapons attack.

FMR. SECRETARY KERRY: Correct, and what I write about is, we paid a price for the way it played out without the red line being enforced by the bombing. But we got the chemical weapons out which was the objective. And did it-cost us.

MARGARET BRENNAN: Even though there have been chemical weapons attacks since then.

FMR. SECRETARY KERRY: Did it, we knew there were precursor chemicals and- and we knew that there was chlorine, which when mixed they still had ability. Those aren't declared. That's just the vagary of the- system by which they measure-

MARGARET BRENNAN: But there have been sarin gas attacks since then--

FMR. SECRETARY KERRY: --chemical weapons. Yes. That is correct.

MARGARET BRENNAN: --under the Trump administration.

FMR. SECRETARY KERRY: Absolutely correct. And I supported President Trump's response to those partially. I supported the use of force, but I don't support just a one-off where you drop a few bombs and there's no follow-up diplomacy and no additional effort to try to use the leverage you get out of doing that. I thought that the president should have done that, President Trump should have done that.

MARGARET BRENNAN: And- you thought President Obama should have done that too.

FMR. SECRETARY KERRY: Yes that's correct.

MARGARET BRENNAN: You were sent around the world to rally support for other countries to stand with the United States to say that this red line on use of chemical weapons needed to be enforced. How difficult was that for you given that the president blinked? He decided not to go through with those military strikes.

FMR. SECRETARY KERRY: Congress was clearly not going to give him the authority that he wanted.

MARGARET BRENNAN: But you thought that the president could have gone ahead with those strikes.

FMR. SECRETARY KERRY: I did.

MARGARET BRENNAN: You are in the book- you write about being surprised when he called you and said, "I'm going to Congress."

FMR. SECRETARY KERRY: I was surprised. I thought we were going to go forward. I thought that weekend was the weekend. I expected the phone call to be telling me that he had decided we were striking that night or whatever was going to happen, and it wasn't. My job was to then affect the president's policy. And I did the best I could in going to Congress and arguing the case. But I do write that we paid a price for that. There's no question about that. We paid a price. And-and all the explanations and everything else doesn't change the perception- and perceptions sometimes are very telling in diplomacy and politics.

MARGARET BRENNAN: You paid a price. You mean- the red line moment has come to for many critics of President Obama define his foreign policy and define it as weak, as not backing up a threat.

FMR. SECRETARY KERRY: For many people that's exactly what I ran into. When I ran into that in the Middle East it was something that I had to push back against for a long period of time. And that's why I say perceptions, but perceptions matter obviously in everything. But I don't think it's fair in terms of the president quote "being weak" because the president took a lot of very tough positions and did a lot of things that evidence strength and that showed a president who had a very clear moral compass as well as very clear, a very clear set of values and principles by which he knew he could protect our country.

MARGARET BRENNAN: But I'm pressing you on this because you write in the book about thinking even now about what you called the open wounds in Syria, that you think almost every day about it.

FMR. SECRETARY KERRY: Well the open wound in Syria is that maybe 500,000 people have now died. It was about 100,000 back in 2013 when the chemical weapons attack took place. It has been an ongoing atrocity, a violation of every sense of propriety, of human rights, of-of diplomatic rectitude. I mean you run the list of things that are at stake in Syria.

It is a sad history for the international community, not just for the United States. It is the failure of the global community to hold a tyrant, a war criminal, accountable for his behavior and to have come together and tried to end the war. What- what- what- I'm proud of is-

MARGARET BRENNAN: He's won that war now.

FMR. SECRETARY KERRY: What I'm proud of is that we continually tried. We never stopped trying. Even when it was tough, even when it looked bleak-

MARGARET BRENNAN: And you took some heat for not stopping trying.

FMR. SECRETARY KERRY: Well yeah, we took heat right up until the end. But that's OK by me. Assad is in the driver's seat today because of what Russia and Iran, Hezbollah, have done. So we have an open wound. Yes a global, an international community owned open wound.

MARGARET BRENNAN: In those days, those very intense days when you were working diplomatically to try to build support to stand with the U.S. and- if they were to go through with a strike. We were at that press conference in London and-

FMR. SECRETARY KERRY: You asked the question, you asked the magic question: "Is there anything that Assad could do?" was your question.

(SOT) BRENNAN: -is there anything at this point that his government could do or offer that would stop an attack? KERRY: Sure. He could turn over every single bit of his chemical weapons to the international community in the next week. Turn it over, all of it.

FMR. SECRETARY KERRY: It turned out to be- the way we solved a critical problem. It was done purposefully in order to put out there a notion without a formal proposal- just as an answer to your question which came at the right moment.

MARGARET BRENNAN: Do you regret that this is the diplomatic off ramp that you ended up with? That ultimately what you strongly believe should have happened didn't?

FMR. SECRETARY KERRY: No, what I regret is that there is- that such an incredibly powerful perception gained a foothold the way it did, that had an impact on people's judgment about what the president was willing to do or not do.

MARGARET BRENNAN: Not enforcing the red line.

FMR. SECRETARY KERRY: Correct. That's- that's regrettable. It's regrettable for everybody. But I- I don't regret putting, you know, the idea on the table and I think it was a terrific outcome in the sense that we got all the declared weapons out of there.

MARGARET BRENNAN: Well because there have been at least two large-scale chemical attacks-

FMR. SECRETARY KERRY: Correct.

MARGARET BRENNAN: --in the past few years.

FMR. SECRETARY KERRY: Well and during which time he's had an opportunity to reconstitute and gain a foothold and there's been no further inspection and nothing else going on.

MARGARET BRENNAN: In our next half hour, we'll get some thoughts from Secretary Kerry about the current President -- and Mr. Trump's efforts to undo the Iran nuclear deal.

MARGARET BRENNAN: Welcome back to Face the Nation, we continue our conversation with former secretary John Kerry.

MARGARET BRENNAN: You spent a tremendous amount of time working to get this deal with Iran for them to freeze their nuclear program. President Trump said this is the worst deal he's ever seen.

FMR. SECRETARY KERRY: Yeah but just saying that doesn't make it that. This is the toughest agreement in terms of inspection, accountability- what Iran was required to do-, with the greatest visibility for the longest period of time of any nuclear agreement on the planet. No country has had to do what Iran did in order to live up to this. But to just walk away while Russia, China, France, Germany, and Britain are all trying to keep this agreement in place. Only the United States walked away, only Donald Trump. So I think that experts who understand- the Defense Department- his defense secretary thought he should keep it. The Secretary of State that he got rid of thought he should keep it. His intelligence people thought he should keep it. The fact is this agreement is working and now it's working without the-

MARGARET BRENNAN: And you tried to save this deal--

FMR. SECRETARY KERRY: --United States. Yes I did.

MARGARET BRENNAN: --Behind the scenes.

FMR. SECRETARY KERRY: Well I try-

MARGARET BRENNAN: And that really angered President Trump. You were calling other foreign ministers. You even spoke with Javad Zarif-

FMR. SECRETARY KERRY: Well at that point in time--

MARGARET BRENNAN: -- the Iranian foreign minister.

SEC KERRY: --foreign policy of the United States was still to support that agreement.

MARGARET BRENNAN: But the president thought you were trying to undermine him.

FMR. SECRETARY KERRY: No, I was trying to have the policy of the United States of America which was part of the agreement to continue and common sense to continue. I didn't negotiate. I spoke out, and I will always exercise my right to speak out.

MARGARET BRENNAN: But President Trump would say he was elected on a platform of exiting this deal. And he went out and attacked you personally because of the phone calls-

SEC KERRY: I- I- I don't --

MARGARET BRENNAN: -- you were making.

FMR. SECRETARY KERRY: -- put any stock in- in that at all.

MARGARET BRENNAN: He said, "John Kerry never walked away from the table except to be in that bicycle race where he fell and broke his leg. That's it."

FMR. SECRETARY KERRY: I did walk away. And we almost walked away on two or three other occasions where we thought it was necessary.

So he really, unfortunately, and I say this sadly- you know, more often than not he really just doesn't know what he's talking about. He makes things up, and he's making that up as he has other things.

MARGARET BRENNAN: Didn't you want to say something at the time? Tweet back at him, at President Trump when he attacks you?

FMR. SECRETARY KERRY: I haven't yet. I think America and our democracy are more thoughtful than dishonest tweets.

MARGARET BRENNAN: Do you think President Trump's unpredictability is or can be an asset?

FMR. SECRETARY KERRY: I would never say no to that. But unpredictability that destroys 70 years of a- a strongly defended message such as NATO, or unpredictability with respect to- what your policy is with respect to nuclear weapons or disarmament or whatever or Russia is not a good thing. There are certain times where unpredictability invites- an overreach by a country.

Secretary Kerry's book was published by Simon & Schuster, a division of CBS.