Critics say the half-day summit, an initiative by Belgian Prime Minister Guy Verhofstadt, risks provoking new rifts in both transatlantic and European relations.

But Verhofstadt told Belgium's RTBF radio his talks with French President Jacques Chirac, German Chancellor Gerhard Schroeder and Luxembourg Prime Minister Jean-Claude Juncker would yield "real and concrete advances".

"If we want to count on the world stage, if we want to avoid the divisions in the European Union that we saw in the Iraq crisis, it is absolutely necessary to have this European defence tool," he said.

"Otherwise, a European Union foreign policy is not credible."

During their two-hour talks, the leaders were to discuss the creation of an EU armaments agency, an idea already backed by the convention on the future of Europe, the body sketching out an EU constitution.

They were also expected to discuss a "solidarity clause" to be included in the new EU constitution, guaranteeing support in the case of an attack on a member state.

A proposal to create a European defence command headquarters outside Brussels could also be on the table, although the leaders have been at pains to dismiss talk of a European rival to NATO.

British Prime Minister Tony Blair issued a thinly veiled warning to the participants on the eve of the summit.

"We won't accept, and neither will the rest of Europe, anything that either undermines NATO or conflicts with the basic principles of European defence we've set out," he said.

Along with France, Britain is one of the EU's few military heavyweights, and observers say its armed forces will need to be at the heart of any credible European defence strategy.

Italy, Spain and the Netherlands have also all expressed reservations about the summit, and helped to ensure that neither EU foreign policy chief Javier Solana nor the EU's current Greek presidency attended.

The four participating countries agree that the deep divisions opened up in Europe by the Iraq war underline the need for the EU to put flesh on the bones of its common foreign and security policy.

But the meeting has fuelled talk of a two-speed EU, at a time when the bloc is struggling to build just the opposite, a Union increasingly united in areas other than the purely economic.

Spanish Foreign Minister Ana Palacio, writing in Tuesday's Wall Street Journal Europe, said the mini-summit could do more harm than good.

"A truly European security and defence policy cannot be achieved by three or four countries acting alone," she wrote in an opinion piece entitled "The wrong way to build consensus".

She added that "if a policy were to be proposed at a time of controversy -- as this one clearly is -- it would become a cause of division within the Union and could prove counter-productive".

The summit, being held at the Belgian foreign ministry, was scheduled to end with a press conference around 12:15 pm (1015 GMT).

SPACE.WIRE