The Tory leader attempted to repair the damage to a bipartisan approach to the conflict, following bitter Opposition attacks on the "gross incompetence" in the bombing of the Chinese embassy in Belgrade, by emphasising that the Conservatives still supported Nato's action.
But Mr Hague - who said on 23 March that a ground force should only be deployed to implement a diplomatic settlement - warned Mr Blair that the air campaign was failing to stop the ethnic cleansing of Kosovo Albanians.
The demands for an urgent decision on the use of ground forces were reinforced by Paddy Ashdown, the Liberal Democrat leader, who said there were only two weeks left to take the decision to send in the ground troops.
Mr Hague told Mr Blair: "It's not only vital that Nato's objectives are achieved but that they are achieved before the first snows of the Balkan winter in October." Mr Ashdown said time was beginning to press hard. "The coming heat of the summer months is going to create a breeding ground for despair if not disease in the refugee camps," he said. "If we are required to use troops to get the refugees back home before the winter, then a decision on deployment is probably going to have to be made within a fortnight or so."
Mr Blair said he "understood exactly" the points being made and insisted there would be no compromise on Nato's demands. But he stressed it would be wrong to say Nato's air campaign was not working, and pointed out that the weather over Kosovo was getting better all the time. "Over the last two weeks our efforts have intensified and the weather in June is better than that in May, and in July better than in June," he said.
The British and US governments have both remained reluctant to deploy ground troops, fearing public support for the war would crumble if there were heavy casualties. But the mood at Westminster was changing decisively in favour of the use of ground forces to hasten the end of the campaign.
Military planners had estimated it would take up to 200,000 troops to fight their way into Kosovo before the conflict, but senior British ministers made clear that the gradual "degrading" of Serbia's forces would enable a smaller ground force to push the Serbs out of Kosovo.
At the Nato summit in Washington last month, ministers privately said it could take four or five weeks of bombing to make a ground assault possible, suggesting that Nato ground forces could be deployed in the first week in June. Javier Solana, Nato's Secretary-General, is due to deliver a report on the use of ground forces.
Conservative insiders said the change of policy had been agreed three weeks ago but Mr Hague was worried that the Conservatives would lose any political advantage from the attack on the Government.
t Downing Street denied there had been a "bust-up" over the war during a 50-minute call between Mr Blair and the Italian Prime Minister, Massimo D'Alema.Reuse content