The idea is for the so-called European Intervention Iniative to be able to lead humanitarian crisis efforts and evacuation operations as well as take on conventional military duties.

The scheme is separate from other EU defence cooperation, meaning there would be no obstacle to Britain taking part after it leaves the bloc at the end of March next year.

"We want to develop cooperation between countries politically willing and militarily capable of acting, when they decide to do so, in different scenarios -- not just military but also civilian," French Defence Minister Florence Parly said after the nine countries signed a letter of intent at a meeting of EU defence ministers in Luxembourg.

"You can't talk about a 'force' to refer to the European Intervention Initiative, because the term is too strictly military and the spectrum for action is much broader," she added, giving the example of British and Dutch rescue efforts in the Caribbean after Hurricane Irma last year.

France, Britain, Germany, Belgium, Denmark, the Netherlands, Estonia, Portugal and Spain all signed up for the EII, which French President Emmanuel Macron hopes will prove more effective than the EU's four military "battlegroups" set up in 2007 but never deployed due to political bickering.

London has always fiercely opposed anything that might open the way to an "EU army" but last month the British junior defence minister Frederick Curzon told AFP the French plan would helo achieve a "deep and special partnership" with the bloc on defence after Brexit.

Paris hopes that a smaller group of countries will be able to act more decisively, freed from the burdens that sometimes hamper action by the 28-member EU and 29-member NATO.

A tenth country, Italy, has also agreed but its new right-wing populist government needs more time to look at the proposal before putting pen to paper, Parly said, insisting it was "a question of details, not substance".

Parly has been at pains over the past few months to reassure the EU, in particular the bloc's foreign policy chief Federica Mogherini, that the French initiative will not compete with the EU's own defence cooperation pact.

NATO chief Jens Stoltenberg played down fears the EII could detract from the transatlantic alliance, which has been responsible for European security for nearly 70 years.

"I see this new initiatve as something that can complement and reinforce the work which is ongoing in NATO to strengthen and increase the readiness of armed forces," he said as he arrived for the talks in Luxembourg.