The man who drives me to and from work is named Woody too. A relief to me, as it minimises the chance of my forgetting his name. I call him Woodman and he calls me Wood. He has become my best friend here, even though he's upset that I have quit drinking beer. He's smart, funny, and there's nothing he hasn't seen in 33 years behind the wheel of his black cab. He drove me for a while before I felt confident he liked me; he doesn't like people easily, especially if they have a rap for busting up black cabs.

Woodman and I agree about a lot of things, but one thing we can never agree about is Iraq. He thinks the only language Saddam understands is brute force. I don't believe we should be bombing cities in our quest for one man. We've killed a million Iraqis since the start of the Gulf war - mostly by blocking humanitarian aid. Let's stop now. Thankfully, most of the Brits I talk to about the war are closer to me than to Woodman. Only your prime minister doesn't seem to have noticed.

I have been here three months doing a play in the West End. I am having the time of my life. I love England, the people, the parks, the theatre. The play is great and the audiences have been a dream. Probably I should just relax, be happy and talk about the weather, but this war is under my skin - it affects my sleep.

I remember playing basketball with an Iraqi in the late 80s while Iran and Iraq were at war. I didn't know at the time that the US and Britain were supplying weapons to both sides. I asked why they were always at war with each other and he said something that stayed with me: "If it were up to the people, there would be peace. It's the governments that create war." And now my government is creating its second war in less than a year. No; war requires two combatants, so I should say "its second bombing campaign".

I went to the White House when Harvey Weinstein was showing Clinton the movie Welcome to Sarejevo, which I was in. I got a few moments alone with Clinton. Saddam throwing out the weapons inspectors was all over the news and I asked what he was going to do. His answer was very revealing. He said: "Everybody is telling me to bomb him. All the military are saying, 'You gotta bomb him.' But if even one innocent person died, I couldn't bear it." And I looked in his eyes and I believed him. Little did I know he was blocking humanitarian aid at the time, allowing the deaths of thousands of innocent people.

I am a father, and no amount of propaganda can convince me that half a million dead children is acceptable "collateral damage". The fact is that Saddam Hussein was our boy. The CIA helped him to power, as they did the Shah of Iran and Noriega and Marcos and the Taliban and countless other brutal tyrants. The fact is that George Bush Sr continued to supply nerve gas and technology to Saddam even after he used it on Iran and then the Kurds in Iraq. While the Amnesty International report listing countless Saddam atrocities, including gassing and torturing Kurds, was sitting on his desk, Bush Sr pushed through a $2bn "agricultural" loan and Thatcher gave hundreds of millions in export credit to Saddam. The elder Bush then had the audacity to quote the Amnesty reports to garner support for his oil war.

A decade later, Shrub follows the same line: "We have no quarrel with the Iraqi people." I'm sure half a million Iraqi parents are scratching their heads over that. I'm an American tired of lies. And with our government, it's mostly lies.

The history taught in our schools is scandalous. We grew up believing that Columbus actually discovered America. We still celebrate Columbus Day. Columbus was after one thing only - gold. As the natives were showering him with gifts and kindness, he wrote in his diary, "They do not bear arms ... They have no iron ... With 50 men we could subjugate them all and make them do whatever we want." Columbus is the perfect symbol of US foreign policy to this day.

This is a racist and imperialist war. The warmongers who stole the White House (you call them "hawks", but I would never disparage such a fine bird) have hijacked a nation's grief and turned it into a perpetual war on any non-white country they choose to describe as terrorist.

To the men in Washington, the world is just a giant Monopoly board. Oddly enough, Americans generally know how the government works. The politicians do everything they can for the people - the people who put them in power. The giant industries that are polluting our planet as well as violating human rights worldwide are the ones nearest and dearest to the hearts of American politicians.

But in wartime people lose their senses. There are flags and yellow ribbons and posters and every media outlet is beating the war drum and even sensible people can hear nothing else. In the US, God forbid you should suggest the war is unjust or that dropping cluster bombs from 30,000ft on a city is a cowardly act. When TV satirist Bill Maher made some dissenting remarks about the bombing of Afghanistan, Disney pulled the plug on him. In a country that lauds its freedom of speech, a word of dissent can cost you your job.

I read in a paper here about a woman who held out the part of her taxes that would go to the war effort. Something like 17%. I like that idea, though in the US it would have to be more like 50%. If you consider money as a form of energy, then we see half our taxes and half the US government's energy focused on war and weapons of mass destruction. Over the past 30 years, this amounts to more than ten trillion dollars. Imagine that money going to preserving rainforest or contributing to a sustainable economy (as opposed to the dinosaur tit we are currently in the process of sucking dry).

I give in to Woodman, and we stop for a few beers. He asks me what I'd do in Bush's shoes. Easy: I'd honour Kyoto. Join the world court. I'd stop subsidising earth rapers like Monsanto, Dupont and Exxon. I'd shut down the nuclear power plants. So I already have $200bn saved from corporate welfare. I'd save another $100bn by stopping the war on non-corporate drugs. And I'd cut the defence budget in half so they'd have to get by on a measly $200bn a year. I've already saved half a trillion bucks by saying no to polluters and warmongers.

Then I'd give $300bn back to the taxpayers. I'd take the rest and pay the people teaching our children what they deserve. I'd put $100bn into alternative fuels and renewable energy. I'd revive the Chemurgy movement, which made the farmer the root of the economy, and make paper and fuel from wheat straw, rice straw and hemp. Not only would I attend, I'd sponsor the next Earth Summit. And, of course, I'd give myself a fat raise.

Woodman drops me at home and I ask if he likes my ideas. He offers a reluctant "yes". As he pulls away he yells out, "But I'd never vote for a man who can't handle a few pints at the end of the day!"

· Woody Harrelson appears in On an Average Day at the Comedy Theatre, Panton Street, London SW1 until November 3. Box office: 020-7369 1731.