Germany, Spain, the Netherlands, Belgium, Denmark, Estonia and Portugal have joined the French-led project -- along with Britain, just as Brexit looms.

A source close to the talks said Finland is also set to join the European Intervention Initiative, known as EI2, which would be independent of both the European Union and NATO.

The meeting comes a day after French President Emmanuel Macron, who has pushed for a more muscular European defence policy since his arrival in power last year, called for a "real European army".

Europe can ensure its own protection against Russia and even, under an unpredictable President Donald Trump, the United States, only through united defence, he said.

"We need a Europe which defends itself better alone, without just depending on the United States," he said.

But the idea of an "EU army" is highly sensitive in member states that jealously guard defence as a matter of national sovereignty.

A French government source later played down Macron's comments, saying that he was not talking about a truly supranational military spanning the continent.

The idea behind EI2 is to be able to rapidly mount a joint military operation, evacuate civilians, or provide aid after a disaster.

Wednesday's meeting is intended to lay out a "roadmap" identifying the nine countries' priorities -- including geographical zones of particular interest -- which senior military officials will develop from Thursday.

"It's about reinforcing Europeans' capacity to act independently to guarantee their security whenever that's necessary," said an aide to French Defence Minister Florence Parly.

Plans for EI2 come as Trump has repeatedly distanced himself from the NATO military alliance, which has underpinned European security since World War II.