It is of the greatest importance that people and governments in many more countries than ours should realize that it is more dangerous to have access to nuclear arms than not to possess them.

Our - our friends can't trust us anymore. You know, Ukraine was a nuclear-armed state. They gave away their nuclear arms with the understanding that we would protect them. We won't even give them offensive weapons.

There is going to be a nuclear arms race in the Middle East if Iran gets a nuclear weapon. And you are going to see it in Egypt, in Turkey, in the Emirates. All of those people will want that.

Issues of energy, climate change, nuclear arms control and non-proliferation are all big deals. These are problems that we have to get right globally, not just nationally, and there are big benefits in cooperating, in terms of sharing costs, in terms of sharing risks, in terms of propagating the best answers.

But scientists on both sides of the iron curtain played a very significant role in maintaining the momentum of the nuclear arms race throughout the four decades of the Cold War.

If Iran becomes a nuclear weapon state it is the end of non-proliferation as we know it. If Iran gets a nuclear weapon you are likely to see Saudi, Egypt and other countries follow suit and we will bequeath to the next generation a nuclear arms race in the world's most unstable region.

In terms of election issues, the urgent challenges we face include securing reforms to de-escalate the nuclear arms race, end voter suppression, improve health care for all Americans and alleviate the climate crisis.

Hiroshima has become a metaphor not just for nuclear war but for war and destruction and violence toward civilians. It's not just the idea we should not use nuclear arms. We should not start another war because it's madness.