War in Europe: This is one campaign that Millbank can't control

Tony Blair had a war room in Opposition. The troops in the bunker in Labour's Millbank Tower headquarters dropped bombs on sleazy Tory MPs, fired cruise missiles at fat cat directors and compiled intelligence reports on the computer Excalibur. This political fighting machine was lean, mean - and, more than anything, utterly controlled.

Updates were mapped out with military precision on a daily general election "grid". The backbench squaddies were kept in order with promises of promotion, or threats of hard labour. Tyrants such as Rupert Murdoch were won over by the whiff of modernity. The Labour leader was so protected that every time he visited a new town, an advance team of researchers would trace his route, scouring the streets for any hint of a negative photo opportunity.

Real war, New Labour has discovered, is far less tidy. When Mr Blair went into his Millbank Tower war room before the general election, he knew exactly what the "theme for the day" was from his advance schedule. When the Prime Minister descends to his real war room beneath the Ministry of Defence, he cannot be sure what Nato will have done overnight. One day it had bombed a convoy of civilians, another time turned the Chinese embassy in Belgrade into a smouldering shell.

The party which got to power and ran the Government by controlling the agenda now has no idea what is going to happen from one day to the next, and this is causing jitters among the strategists at Downing Street. They know that the Prime Minister's reputation rests on victory over Slobodan Milosevic, but they are utterly powerless to ensure that this victory is delivered. These are the people proud to be control freaks, because they believe it is their job to protect the New Labour "project" at any cost.

Yet now they are dependent on factors which are out of their hands - from the weather over Kosovo to the identification of targets. In opposition, it is claimed, Labour would never have allowed the type of human error which led to the bombing of the Chinese embassy to have occurred; it would have made sure that three separate researchers checked that the map of Belgrade was up to date. Mr Blair is said to be increasingly frustrated by working in coalition with other Nato countries, an alliance in which decisions are taken by committee and everybody has to rely on people they do not know.

The Prime Minister has made much of leading the international charge against the Serbian leader. He is motivated by a simple desire to see, as one aide put it, "good triumph over evil". But he has stuck his neck out beyond other heads of state, and this is a huge gamble.

If the military campaign works, Mr Blair will be the international hero, his place as world statesman firmly established. If it all goes wrong, or Nato has to do some sort of deal with President Milosevic, Bill Clinton will be able to walk away, shaking his head sadly at the cameras. Mr Blair, on the other hand - who in the latest example of hawkish rhetoric last week promised "no compromise, no fudge, no half-baked deals" - will look at best naive.

This is convenient for Mr Clinton, whose advisers privately admit that they are delighted that the Prime Minister has been the outrider, pushing other countries to accept the need for ground troops, so that their man can if necessary come in behind and look moderate. It is also useful for the Conservatives, who last week sought to exploit Mr Blair's discomfort over the Chinese embassy bombing, with William Hague scoring some political points at Question Time.

But it is a high-risk strategy for Mr Blair. He has taken his hardline stance partly because he can - he does not face the same opposition as Gerhard Schroder does in Germany from his coalition partners in the Green Party or Bill Clinton does in the US from his political enemies. He has also stressed the importance of fighting this "progressives' war" because he must to keep his party on side.

But Downing Street has become increasingly aware that this strategy risks leaving Mr Blair politically exposed. His initial categorical statement that the international community had a duty to prevent a humanitarian crisis was clarified, during his trip to Chicago, by a more measured speech, setting out the parameters within which the "goodies' police force" could act.

Alastair Campbell, the Prime Minister's Press Secretary, now spends half his week in Brussels, concentrating on directing the media operation at Nato headquarters. This is no coincidence. He knows that if the campaign backfires, Mr Blair's apparently unstoppable success in the polls could finally be challenged. New Labour is trying to get things back under control.