Is it always a journalist's duty to report the truth, even if it may damage innocents?

I'm a total First Amendment Jeffersonian. It's their job to keep it secret and my job to find it out and make it public. But once one gets someinformation, one doesn't run pell-mell into it. You know, maybe six or seven times in 40 years I've had a story and the president has called up and said: "If you write this story, American security will be damaged." In every case except one, we wrote the story. And son of a bitch, the Russians didn't launch paratroopers into the foothills of San Francisco the next day.

Are there times when you have a scoop, or a piece of information, but let it go?

You're constantly not publishing everything you know. That's part of the game.

Do you ever worry that your phone is bugged?

Some people I only talk to in their home or their office, but I arrange the calls here. To bug me legally they'd have to get a warrant; once you have something illegally you can't use it very much. If the 9/11 attacks taught us one thing, it's that the agencies collect lots of wonderful stuff they don't share with anybody.

You rely a lot on unnamed sources. Is that a dangerous technique, or an invaluable one?

Look at the serious press in the UK, France, America: every single day there are unnamed sources. But I believe people in my profession should be held to an extremely high standard. I welcome the fact that people can sue me.

Do you find the libel laws in the UK chilling?

There's no question - D-notices are chilling. You guys have a very tough system.

Isn't there a risk that some high-level sources might be "playing" you?

Of course, that's a categorical risk. But I consider myself a full-service agency. You can come to me with a secret and I take it to other people and learn things about what you know. Then I write a story that includes things you didn't know.

So when the government assesses what I wrote to see who could have leaked it, you're not ever considered, because you could not have known what was published. It's foolproof.

How have you managed to remain an outsider for so long?

There's no way they would deal with me. The Obama White House can't abide me. Within a month, they were going behind my back to my editor: "What's your man Hersh doing?"

What do you make of Barack Obama?

Don't get me going on Obama. If he decided to be a one-term president, he could be marvellous, but it's not clear he's decided that.

Did he deserve the Nobel Peace Prize?

Well, no, of course not. The question is: will he stay in Afghanistan until he thinks it's the right time to get out politically? Or is he going to take a chance of not getting re-elected and find a way out quickly? It's not such a hard way out. There are people to talk to there.

On Iran, are we repeating the mistakes that were made on Iraq?

Some of the things are very disturbing. We are getting new leadership at the International Atomic Energy Agency. The next wave there is not going to be as rational. It's amazing to me, as someone who went to the Vietnam war and Iraq war, and now the Afghan war. There's simply no learning curve.

Post-Bush, do you think there's still a risk of a military strike on Iran by Israel or the US?

Yes.

Where do you place yourself on the political spectrum?

I'm your standard left liberal, but I vote for Republicans, I've given money to them. I'm not a pacifist. I would have been tough on Osama Bin Laden after 9/11. But I'd have done it legally.

Are you disappointed Obama didn't release those "torture pictures"?

His position is that, at a time when we have 130,000 Americans in Afghanistan, putting the pictures out would just inflame people to take action against them. The New York Times has been editorialising against him, but when it had a reporter captured, it thought it was perfectly appropriate not to talk about it publicly for seven months, on the grounds that the paper was trying to protect his life.

What would you like to forget?

My Lai.

How would you like people to remember you?

I couldn't care less. I don't believe in life after death.

Are we doomed?

The trouble is that hope sprang anew in America last November. And I think the dashing of that hope is going to be much more lethal than even the cynicism under Bush and Cheney. If that hope is dashed, we'll really be in trouble around the world.

Interview by Mehdi Hasan