Antoine Bouvier, chief executive of missile maker MBDA, said failure to agree on a "new association" on defence could have significant negative implications for both sides, as well as the United States.

"Without the UK, with its capabilities, technologies, industry and programmes, we the remaining 27 states will have more difficulties to achieve critical mass in terms of budget, in terms of industrial capabilities," Bouvier told Reuters in an interview at the Paris Airshow.

"So we will have to find a way to maintain the right access for the UK to the EU defence initiatives," said Bouvier, whose company is owned by Airbus Group (>> Airbus SE), Britain's BAE Systems Plc (>> BAE Systems) and Italy's Leonardo Finmeccanica SpA (>> Leonardo - Finmeccanica).

EU leaders are meeting in Brussels on Thursday and Friday to discuss defence, security and other issues, including Brexit.

EU Commission President Jean-Claude Juncker this month urged EU governments to forge a tighter military alliance, given Britain's decision to leave the bloc and U.S. President Donald Trump's lukewarm stance on the Washington-led North Atlantic Treaty Organisation.

Although the EU has more than a dozen military missions abroad, the world's biggest trading bloc has never been able to match its economic might with broad defensive power, preferring to rely on NATO instead.

Monika Hohlmeier, a German member of the European Parliament and chair of the Sky & Space Intergroup, told Reuters she was open to Britain remaining engaged in defence and security matters, but only if it stopped blocking EU initiatives.

"There can't be the cherrypicking that we've seen in the past," she said. "The Britons have to make up their minds where they want to participate, and then they have to contribute."

France, Germany and Italy want ways to pay for common military missions abroad, to be able to use EU battlegroups for the first time and for industries to collaborate and develop weapons and helicopters that can be used by all EU armies.

(Reporting by Andrea Shalal; editing by John Stonestreet)

By Andrea Shalal

Stocks treated in this article : Airbus SE, Leonardo - Finmeccanica, BAE Systems