The EU force is designed to maintain stability in Kabul
He said the force was being created by the EU and described the decision as "a turning point in the history of the European Union".
However, UK Europe Minister Peter Hain said it was wrong to suggest that the force was a European initiative.
"It is an international force which Europe is giving full support to," he said.
UK 'to lead force'
Military officials from several European countries, together with the United States, Jordan and Turkey are holding a separate meeting in London to discuss the formation of the Afghan force.
German Foreign Minister Joschka Fischer told reporters: "Even if we wanted to (establish an EU force), we could not do it. This is an issue that will be handled in the UN Security Council."
The UK has already indicated that it would be prepared to lead the stabilisation force.
The aim of the force would be to maintain stability in and around the Afghan capital, Kabul, as a new interim government takes power in just over a week's time.
US Secretary of State Colin Powell said in London on Tuesday that the stabilisation force would be quite separate from the US force hunting for Osama Bin Laden - disappointing some US generals, who had hoped to control both operations.
The EU has been working for two years on a security and defence policy, involving the creation of a 60,000-strong rapid reaction force, which the summit is to declare "operational".
European armies have considerable experience of peacekeeping in the Balkans and the Middle East, but the EU's foreign policy chief, Javier Solana, said the Afghan operation would be "more difficult than other peacekeeping missions in the past".
EU leaders hope that during the summit they will be able to persuade Greece to drop objections to a deal with Turkey that would allow the rapid reaction force to make use of Nato military planning capabilities.
Turkey, a member of Nato but not of the EU, had initially vetoed this, but was won round round by a promise of consultation on a case-by-case basis.
Greece now argues that Turkey is being given too much say in EU affairs.