SADDAM Hussein is undoubtedly a major threat to his own people and to the rest of the world.

When US Vice President Dick Cheney arrives in London today to talk to Tony Blair, he is expected to press for Britain to support a large military attack on Saddam.

Mr Blair, who played an important part in restraining George Bush's bellicose instincts immediately after September 11, will have to think long and hard before offering that support.

He must convince himself that America has achievable goals. The Gulf War petered out, leaving Saddam still in power and leaving the allies saying they would encourage opposition within Iraq to topple him. This hasn't happened because Saddam has ruthlessly removed all opposition.

So this time around, Mr Blair must convince himself that Saddam can be reached, and that a viable government can be found to replace him. Even in Afghanistan, where there was a strong alternative to the Taliban in the form of the disparate elements of the Northern Alliance, building a new government out of the wreckage of a war-torn nation has proven so difficult that the West will be required to support it militarily for a decade. It will be even more difficult in Iraq - so while Saddam does threaten the stability of the world, Mr Blair may wonder whether deposing him will make the world an even less stable place.

Mr Blair will also have to ask himself how many countries will give their full support to American action against Iraq, particularly if Mr Bush continues to produce short-sighted unilateralist actions from his hat like last week's steel levy. That angered Russia, Australia and the rest of Europe - America's most important allies in any military attack.

Mr Blair will have to ask Mr Cheney to produce real evidence to link Saddam with al-Qaida and September 11. While Saddam is guilty of many things, supporting Osama bin Laden appears not to be one of them - yet if this phase two of the war against terrorism is going to have substantial support in the wider world, it will have to appear - and be - legitimate.

Finally, Mr Blair will have to ask Mr Cheney what America is doing to resolve the world's biggest threat to stability: the conflict between the Palestinians and the Israelis. Just sending envoys to the Middle East is not enough; America must now start banging heads together.

Unless these two senseless sides can be brought together, an attack on Iraq is likely to enflame the situation. Saddam will lob a Scud into Israel, become the champion of the Arabs, the Israelis will retaliate with even more venom, and...

Mr Blair must convince himself, his party and the country as a whole, that the Americans have really thought this through.