NATO Secretary General Mark Rutte on Monday warned the European Union not to create “barriers” that would prevent companies from NATO countries outside the bloc from participating in its defense industrial project, Reuters reports.

The European Commission last year put forward a proposal to spend 1.5 billion euros to give countries incentives to jointly buy from European firms and encourage industry to build up capacity.

However, member states have yet to agree on how much of the funds should be set aside for EU companies.