Three good reasons to exercise caution: Douglas Hogg responds to the call by Paddy Ashdown in yesterday's Independent for action from the West to relieve the siege of Sarajevo

IHAVE been reading Paddy Ashdown's articles during his visit to Sarajevo. I have just returned from a visit to Bosnia with Malcolm Rifkind, visiting the British forces with the United Nations Protection Force. We spoke to a wide range of UN troops, including the Unprofor Commander, General Cot. I was struck that their unanimous advice directly contradicts much of what Mr Ashdown has been saying.

Paddy Ashdown states that Sarajevo faces humanitarian disaster this winter. On this point, he is right: the position is indeed extremely serious. The prospects for those living in the city - who have already suffered so much - are appalling. The intensified violence and the imminence of winter make it all the more urgent that a way be found to bring this bloody conflict to an end.

It follows that the highest priority - and I believe Mr Ashdown also accepts this, although in his articles he places less weight on the Geneva talks than would I - is to achieve a lasting and equitable peace. This can be done only through a negotiated settlement agreed by all three warring parties. David Owen and Thorvald Stoltenberg are continuing their efforts to bring the parties together. It is an enormously difficult task but, despite the odds, they have made some progress. Last week, constitutional arrangements for a union of Bosnian republics were agreed. The main question is now the map. There has been progress on this also, but much hard bargaining remains to be done.

What is now crucially important is that all three sides should persist in the negotiations. The Bosnian Serbs are being pressed hard to make concessions, to ensure that the Muslims have a viable territory. Sanctions on Serbia are having a dire effect on the economy: inflation last month was more than 500 per cent. Belgrade, too, faces a bleak winter. But the Bosnian Serbs are continuing their attacks around Sarajevo in order to tighten their grip on the city. They must understand that, if they continue to strangle Sarajevo, they face the prospect of air strikes. Nato is drawing up plans for such strikes. It is our strong hope that the Serbs will heed this warning and that this additional element of pressure will help to bring the negotiations in Geneva to a successful conclusion.

The Bosnian Croats must understand that they will have to concede territory, in particular to ensure that the Muslim- majority republic has access to the Adriatic Sea and to the Danube; the Croatian government has been warned that it must stop its military interference in Bosnia or face sanctions.

If an acceptable peace settlement can be achieved, that surely must be better for the Bosnian people than prolonged war. They must not continue to hold out in the vain hope of Western military intervention on their side. This has never been realistic: no government is prepared to provide the massive numbers of troops that would need to be deployed on the ground, for an indefinite period, to impose peace on the combatants. And this would not solve the problems that caused the civil war.

Paddy Ashdown argues that the UN should use force to fight aid through and to ensure the withdrawal of Bosnian Serb heavy weapons from within range of Sarajevo. He makes it all sound very simple. It isn't. These ideas are not new; we have examined similar options before. With our Nato allies we are now taking a fresh look at the alternatives. There is no doubt that the stakes are higher than ever. The negotiations have reached a critical point, but if there is no peace, Sarajevo and the other enclaves in Bosnia face a ghastly winter. We must judge how we can best help bring about peace and sustain the vital humanitarian effort. A resort to force has never been ruled out. But the advice of everyone I met in Bosnia, including the Unprofor commander, is that we must be cautious, for three reasons.

First, every UN soldier in Bosnia and Croatia - more than 20,000 including the 2,400 British troops - is within range of Serb artillery. These soldiers are not deployed for battle but to carry out humanitarian work. If the UN attacks the Serbs, the Serbs could retaliate immediately by shelling British, French, Canadian and other UN forces. Aid workers, European Community Monitors and others are also vulnerable.

Second, the UN humanitarian operation relies upon its neutrality to deliver essential relief. The UN forces are entitled to use force in self-defence, and do so when necessary. But it is unrealistic to believe that the aid can be fought through by force. This would involve UN forces on the ground engaging one or more of the warring parties (the main obstacle to the aid convoys from Split to Sarajevo - as Mr Ashdown has acknowledged - is not the Serbs, but the fighting between the Croats and Muslims in central Bosnia). This would draw the UN inexorably into the ground war, requiring massive reinforcements of ground troops which, as I have said, no government is ready to provide.

Third, we need to be clear about our priorities. The people of Sarajevo, and many others throughout Bosnia, are being kept alive by the UN relief operation, which saved hundreds of thousands of lives last winter. More than two million people in Bosnia are now dependent on UN supplies. Our present efforts are admittedly vulnerable, but British UN troops have succeeded in delivering over 50,000 tonnes of supplies of aid. The RAF Hercules in the airlift to Sarajevo has brought in nearly 10,000 tonnes. That effort is continuing today; supplies are still getting through. It is extraordinarily difficult and dangerous work, but it is saving lives.

The writer is Minister of State for Foreign and Commonwealth Affairs.