Parliament - The Sketch: Cook mans the Nato ramparts but the edifice cracks

"WE SHOULD not regard the peace process as a zero-sum game, in which if somebody wins someone else must lose," said Robin Cook sagely. It struck a very statesmanlike note this - recognising that adversaries must come to see concession as a mutual gain, rather than a personal defeat.

Mr Cook was talking about Israel, of course, not Kosovo, where the government remains adamantly committed to a zero-sum game. Asked later whether there were any circumstances in which the Serbian President's removal from office would be added to Nato's list of objectives Mr Cook answered no, but he did so in terms that implicitly enlisted the Serbian people as agents of a final retribution. His policy must not just be reversed, said Mr Cook, it must "be seen by his people to be reversed". Mr Cook, I feel sure, must have fantasies of Slobodan Milosevic hanging upside down by his his ankles outside a Belgrade petrol station.

I can't help thinking of the Foreign Secretary over the past few weeks as a man besieged, which might seem slightly perverse given that he represents one of the more enthusiastic investing powers. On the other hand Mr Milosevic doesn't have to defend publicly his policy against hostile and often well- informed comment.

At first the Government's redoubt looked immensely secure. Above the battlements waved a large banner emblazoned with the words "Imminent success" and it was around this standard that Mr Cook rallied his troops. He was probably heartened by the fact that the besiegers were an ill-assorted crew - Baron Clark on the right flank, catapulting putrefying horses into the keep in the hope of spreading disease, Friar Benn and Father Dalyell on the left, taking it in turns to hurl pious warnings of doom through the portcullis. And the massiveness of the fortifications - not a chink in the masonry of Nato will - must have reassured him further. It would all be over within weeks.

But it wasn't. Two months on and that standard is looking rather tattered; the word "Imminent" was shot away sometime in the fourth week and the word "success" has long lost its first bright definition. When Mr Cook asks the defenders to salute the flag these days there are sceptical mutterings in the ranks.

"It's no use pretending in the eighth week that the objectives have been achieved or that we are close to achieving them," said Michael Howard yesterday, representing the Tory contingent who find themselves trapped inside the castle and obliged to defend it too.

And there are other problems. The molten lead has a nasty way of splashing back on those pouring it, reducing their zeal in combat. Such accidents are inevitable in a modern siege, says Mr Cook, but it's a poor ointment for the burns. What's more, the Foreign Secretary is beginning to wonder about that outer wall, which once appeared so impregnable but is now beginning to show evidence of cracks. The Italian stone, in particular, seems worryingly friable. He must continue to assert its strength while at the same time planning a retreat to the keep.

There are signs that this is already under way. The rhetoric now is not "We will soon prevail" but "We cannot afford to lose". As promises of victory ring increasingly hollow to the defenders, Mr Cook must rally them by other means - chilling their blood with tales of the enemy's ferocity. The Serbs "may now have killed twenty to thirty thousand men, women and children", he said yesterday, prefacing an anthology of fresh atrocity stories. This undeniably has its effect - stiffening the resolve of those inside the walls - but the doubts are getting louder and more coherent. Mr Cook will not say anything to sap morale but he must be praying that some kind of relief will appear over the horizon soon.