"The threat of war may not be imminent, but it is not impossible," commission chief Ursula von der Leyen said last week, adding: "It is time for Europe to step up."

There was an "urgent need to rebuild, replenish and modernise member states' armed forces" after decades of trimmed budgets following the Soviet Union's collapse in the 1990s, she said.

The war in Ukraine has forced Brussels to innovate, and an EU defence strategy to be presented Tuesday by commissioner Thierry Breton borrows from some mechanisms already put in place.

These include the bloc's Act in Support of Ammunition Production (ASAP), which according to Breton will swell the number of shells produced annually in the EU to two million in 2025 against a quarter of that figure when Russia invaded Ukraine in February 2022.

"We are doing it with artillery munitions, we must now be able to do it for all equipment necessary for our security," Breton said.

The commission will propose favouring common purchases of weapons made in the European Union.

That would change the scenario since the invasion of Ukraine, in which nearly 70 percent of arms bought by European nations and sent to Kyiv came from the United States, an EU official said on condition of anonymity.

An overall aim is to make up lost ground and see Europe's defence industry become as competitive as that of the US.

Brussels will suggest a European mechanism for arms sales similar to the US one.

- Weapons stock -

The commission will also suggest creating a "catalogue" so that EU countries can be aware of what other members' defence industries can offer, the EU official said.

The United States possesses a strategic reserve of weapons -- a war reserve stock -- that it can call on in urgent moments.

The EU wants to create a similar weapons stock, so that its defence industry can be just as reactive as its US counterpart.

The EU official said the defence manufacturing sector also needed better visibility for investment and production, which would require firm orders made over longer terms.

Part of the EU proposal is based on how the commission spearheaded the acquisition of Covid vaccines during the coronavirus pandemic.

At the time, the commission advanced money under joint procurement contracts that allowed EU countries to ramp up production in their borders, the official said.

The commission also wants to participate in major EU defence projects to defend space, digital connections and, after the sabotage of gas pipelines in the Baltic in September 2022, seabeds.

These "bold decisions" will require "political courage", von der Leyen, a former German defence minister, said.

For Breton, there will also need to be "adequate budgetary ambition", and he has advanced a figure of around 100 billion euros ($110 billion).

Some EU countries, including France, are suggesting common borrowing as happened during the Covid pandemic.

But other countries, like Germany, view that as unnecessary.

To defuse the debate, von der Leyen has suggested using windfall profits generated from Russian assets frozen in the EU, which Greece's special envoy for Ukraine Spiros Lampridis said could come to 50 billion euros.