Barack Obama: “It's time to send a clear message to the world: America seeks a world with no nuclear weapons.”

When we choose, when we make that decision, I do believe – and there is evidence for this – that the world gets incrementally better, and that is a worthy goal and it’s worth fighting for.

People need to “rediscover what’s the story we tell about how we’re going to live together, and see each other, and recognise each other, and disagree, and yet, still care for each other”.

I think when we act on that basis, it doesn't always work out, but over time things do get better.

And I will fight for that, even if I don’t always think it’s going to win.