NATO and the European Union are partners in defence, not rivals, top officials said Thursday, downplaying any suggestion EU military ambitions might undermine the US-led alliance which has protected Europe for decades.

‘I strongly believe it is absolutely possible to strengthen European defence without duplicating efforts by NATO,’ alliance chief Jens Stoltenberg said.

‘EU leaders have (also) conveyed that this is not about the EU doing collective defence, the EU building structures that would compete with NATO,’ Stoltenberg said after EU foreign affairs head Federica Mogherini met NATO defence ministers in Brussels.

Mogherini has drawn up a Global Strategy which says the EU should seek ‘strategic autonomy’ to face multiple security threats, ranging from conventional to hybrid warfare, from the Ukraine crisis to Syria, from poverty in Africa to massive migrant flows.

Her proposal for an EU military headquarters in Brussels -- also home to NATO's HQ -- has especially sparked concerns that the bloc is seeking a more independent role.

Mogherini on Thursday insisted this was not the case at all.

‘Let me clarify that immediately -- I have to do that again and again -- first of all we are not planning a European army,’ she said as she arrived for the defence ministers meeting.

‘We are not planning to have any headquarters, as for instance NATO has SHAPE,’ she said, referring to the alliance's military HQ.

At the same time, Mogherini said the EU does have civilian and military operations, such as in Africa or in the Mediterranean, and needs to improve command and control centres to run them.

‘But this can be done ... without any kind of overlaping or duplication with NATO,’ she said.

Britain, a major power itself, has traditionally opposed any idea of a European army or EU military arm but after the shock Brexit vote, France and Germany said the bloc should be more ambitious.

Britain's defence minister Michael Fallon said Wednesday there could be no question of the EU taking on NATO's collective defence mantle, and there was ‘very strong opposition to that kind of duplication’ in the bloc.

German Defence Minister Ursula von der Leyen meanwhile said there was room -- and benefit -- for both in an increased EU defence effort.

‘I will make clear that NATO and the European security and defense union have different profiles and different tasks but that we need them both,’ von der Leyen said.

‘It is important that we do not build double structures. I will emphasise again that we are not talking about a European army,’ she added.