Saddam Hussein raised a dyed black eyebrow when I asked him last week in an underground bunker in Baghdad if he'd seen the picture of the British Foreign Office minister, Mike O'Brien, kissing Colonel Gadafy under the canvas on a Mediterranean beach. As well he might. Here was the ultimate example of preferring jaw-jaw to war-war, in Churchill's famous phrase. In the not too distant past, Gadafy armed and financed terrorists to blow up British cities, while his men shot dead a policewoman in a London street and have been held responsible for the biggest act of mass murder, at Lockerbie, in British criminal history. Yet, rightly in my view, the Foreign Office has concluded that we can't choose who rules Libya and would be better off talking to those who do.

Iraq, on the other hand, has never harmed Britain. Indeed, Britain helped arm the Iraqi dictatorship to harm others, including Iran and Iraq's own Kurdish population, while people like me were demonstrating for human rights outside Saddam's Tottenham Court Road "cultural centre" in London. Yet now it seems only war-war can be contemplated for Iraq - even a war in which perhaps tens of thousands will die and the Middle East be plunged into chaos and bloodshed.

O'Brien's attempt to square this circle contained a masterpiece of doublespeak. Libya, he said, was moving towards compliance with international law, while Iraq was moving in the opposite direction. This came in a month when Iraq had offered access for British experts to inspect suspected sites of weapons of mass destruction; invited the US congress to do the same; asked Hans Blix, head of the UN arms inspectorate, to come to Baghdad for talks on "the next stage" of inspections; and, most crucially, declared it "accepted and would implement" all UN security council resolutions (which contain the demand for unfettered access to Iraqi sites) concerning their country. And it comes after more than a decade of war and sanctions - which have cost the lives of a million Iraqis - during which not a single act of international terrorism has been proved to emanate from Baghdad.

These diplomatic moves by Iraq would, in a sane world, be followed up and put to the test. They represent all that the British government, at least, has been asking for. After all, if their sincerity was found wanting, what would the US government have to lose? It would still be the world's only superpower, able to invade countries and overthrow governments with impunity, and would be doing so having gone the extra mile for peace, with a strengthened international consensus behind it. That Bush shows every sign of trampling on the olive branch gives the lie to any claim that the only interest is in Iraqi disarmament.

We can understand that Bush, elected against the popular vote and courtesy of a distinctly Takriti-style fix, insists on picking other people's presidents. Thus he has ordered the popularly elected Palestinian president Yasser Arafat into the dustbin of history and now insists the Iraqi president must follow. But who next? The mullahs' regime in Tehran, the unstable autocracy in Saudi Arabia, the Ba'ath party dictatorship in Syria, its neighbour Lebanon - home to Hizbullah - or the heavily armed communist state of North Korea? This is a recipe for endless war and global turmoil. It is also a recipe for a proliferation of terrorism and the creation of thousands of Bin Ladens throughout the Muslim world and beyond.

In my meeting with the Iraqi president last week, he seemed to believe that our own government, with its special relationship to Washington and its more nuanced take on Arab affairs, might be the one to break the log jam. Seeing Britain as Greece to America's Rome, many Arabs feel that Britain - the older though faded power - might guide the gunslinging Americans back to the negotiating path and adherence to UN resolutions and international law.

Mr Blair would be doing himself as well as the world a favour if he picked up this possible role. The stakes could not be higher. Some of Britain's oldest friends in the region may well be swept away in the aftermath of a quarter-of a-million-strong "crusader" invasion of an Arab Muslim country: friends with whom Britain maintains a trade surplus of many billions of pounds; friends who sit on top of the worlds largest oil fields, the interruption to whose production could easily lead to ballooning prices and deflating western economies. In the age of Arab satellite television, every burning building will illuminate every home from the Atlantic to the Gulf and each picture of the ribbons of Iraqi civilians being swept from the inferno will inflame an already seething Arab world.

If it comes, this will be a war of movement rather than position. There will be no Iraqi lines stretched across the desert waiting to be cut down, indeed no battlefields as such. This will be a war of the cities, where invader, defender and civilian population will be up close. Saddam warned me that if the invader came, he would be resisted from street to street. He pointed to the fate of Sharon's army bogged down in a tiny part of Palestine against a small, largely unarmed population. Many Iraqis would cheer the downfall of Saddam, but many - especially in the central Sunni heartlands - would be likely to rally to defend their country. Enough of the Republican Guard, the Saddam militia - potential suicide bombers, every one - the volunteer "Jerusalem Army" and the armed membership of the Ba'ath party can be expected to ensure high casualties and make the whole operation a potentially fatal gamble.

And then there's trouble ahead at home. Mr Blair is nothing if not a skilled sniffer of the political wind. He knows that a gale of laughter is the British people's response to the idea of their fate being in the hands of George Bush. He knows that, from the cabinet peak to the foothills of the labour movement, there is massive, perhaps critical disagreement with his "we'll follow the old man wherever he wants to go" attitude to the US Republican leadership. He is well aware that ministerial resignations and a full-scale parliamentary whirlwind - likely to be foreshadowed at the TUC and Labour conferences - lie ahead if he joins the new crusade.

The public is making its voice heard in opinion polls, petitions, on radio phone-ins and in letters columns. Never has Mr Blair been in such a comprehensively losing position on any political issue. If he joins this absolutely illegal, immoral and counterproductive war, not only will he not be doing so in our name: he may find he will soon cease to speak for us on anything at all.

George Galloway is Labour MP for Glasgow Kelvin and senior vice-chairman of the parliamentary Labour party foreign affairs committee. He is a columnist for the Scottish Mail on Sunday.
Guardian special report Iraq

Guardian Iraq archive