For while Nato leaders in Washington make speeches praising the foresight of the organisation's founders, many people are asking "Has Nato miscalculated over Kosovo?"

An investigation by BBC television's Panorama programme has revealed that while the West engaged in diplomacy with Yugoslav President Slobodan Milosevic, the intelligence community delivered warnings that he was already planning a programme of ethnic cleansing.

Failed diplomacy

Nato's leaders say that last year they tried everything to bring an end to fighting in Kosovo - and hoped they had succeeded in brokering an October 1998 ceasefire.

Critics say Nato was woefully unprepared for refugees

But while the West tried to sustain the peace over the winter and persuade the two warring sides to sign a peace accord at the French chateau at Rambouillet, some say that preparations for the subsequent escalation of the conflict were inadeqaute.

Porter Goss, chairman of the US House of Representatives' Intelligence Committee, told Panorama: "In February 1999, the head of the CIA, George Tenet, briefed congressional leaders after the order to prepare for war.

"He said that military action could include the chance of ethnic cleansing. The policy makers were not misled by any analysis or analytical picture.

Gen Wesley Clark: "This is the way the Nato leaders wanted it"

"If we stuck a stick in this nest, we would stir it up more," he said.

"Instead of caving in, Milosevic struck back harder and more ruthlessly against the Kosovo Albanians.

"The intelligence community predictions were accurate."

Operation Horseshoe

Operation Horseshoe: Panorama asks how much Nato knew

In January, international monitors accused Serb forces of the massacre of more than 40 civilians in the village of Recak, an atrocity that hastened the pace towards air strikes.

While Nato sent envoys to Belgrade to try to restore the October ceasefire, evidence gathered by Panorama reveals that the West had obtained knowledge of a plan of systematic ethnic cleansing, known as Operation Horseshoe.

Rudolf Scharping, Germany's Defence Minister, said: "The clear objective (of Operation Horseshoe) was to ethnically cleanse Kosovo and remove the whole civilian population.

Rambouillet: 'Milosevic treated it as theatre'

"The operation was prepared by President Milosevic and his regime. It was organised at November 1998, started during the Rambouillet negotiations and intensified after the talks ended."

While General Wesley Clark, Nato's supreme commander of European forces, has denied knowing of Operation Horseshoe, John Scanlon, former US ambassador to Belgrade, said that President Milosevic regarded the talks as nothing more than political theatre.

"President Milosevic's behaviour throughout was that he did not take it seriously," he said.

"I don't think that he even intended singing the agreement."

Military hamstrung

While second-guessing Belgrade presented its own problems, critics say military plans were seriously compromised when leaders ruled out using ground forces.

Paddy Ashdown: 'You have to keep your enemy guessing'

"In my view it was wrong," said Paddy Ashdown, leader of the UK's Liberal Democrats and a former British army Special Forces officer.

"It could not be done without ground troops. I suspect that Nato planners knew this.

"One of the things you do not do when you have an enemy in war is exclude any possibility. You keep them guessing.

"But Milosevic could then say, well this is something that is not going to happen.

Paddy Ashdown: "This cannot be done without ground troops"

"That left him room to manoeuvre for the terrible ferocity we saw."

General William Nash, a former US commander of Bosnia forces, added: "The lack of ground options gave Milosevic a view of the limit of our determination.

"But operationally, it allowed him to disperse his forces and make it much more difficult for the air forces to find and attack them."

US politicians have been among the more vocal critics of the policy of gradual escalation in air strikes.

One described the campaign as "bombing-lite" and both President Bill Clinton and Secretary of State Madeleine Albright have come under scrutiny.

The President, mired in the impeachment hearings, missed a crucial meeting in January when Mrs Albright put forward her proposals for limited Kosovo autonomy backed by troops - the basis of Rambouillet.

The Secretary of State has also been accused, most notably by "diplomatic insiders" in the Washington Post, of prosecuting a personal conflict born out of childhood experiences as a refugee.

Endgame

Nato leaders deny that they are attempting to fight a "painless war" to try and keep the wide alliance together.

Infrastructure targeted: Fears for Serbian stability

But while there are signs that some Nato leaders are moving towards ground intervention, questions remain over what the endgame will be.

US Senator Pat Roberts, member of the intelligence and armed forces committees, said: "Gen Clark needs to be given full authority to run this war.

"The tactics are not being dictated by the intelligence.

There will be no peace until Milosevic is removed from power."

While some leaders are calling for President Milosevic to go, others believe that he should still be negotiated with.

Analysts also say that as the bombs continue to destroy Serbia's infrastructure there are serious implications for the country's long-term stability.

"The question is being asked, what if the bombing does not work," said Porter Goss. "The answer has always been blurred."

Whatever the future of the region, a judgement has to be made soon about ground troops, said Paddy Ashdown.

"I have been at the other end of the line as a soldier," he said. "Politicians should not be taking these decisions."

"Nato believed it could bomb President Milosevic into submission. I have always thought that unlikely. We should be planning for Plan B - to use ground troops - when it is possible to do so.