Speaking at a meeting in the Slovakian capital Bratislava on Tuesday, UK Defense Minister Michael Fallon told his 27 counterparts that the UK would "continue to oppose any idea of an EU army or an EU army headquarters which would simply undermine NATO."

Fallon's comments followed a meeting earlier in September in which EU leaders met without the UK for the first time since the EU referendum. Europe was left stunned on June 23 when 52 percent of the UK voted in favor of leaving the EU.

The first post-Brexit vote summit saw the EU leaders agree on a six-month roadmap to create a new "vision" for the EU. Included in the plan was an increase in joint military efforts between the block - something which the UK has repeatedly opposed.

'Underminig NATO'

Asked on Tuesday whether the UK could veto the plans while it still remains a member of the EU, Fallon said: "There is no majority here for a EU army."

"There are a number of other countries who believe with us that [an EU army] cuts across the sovereignty of individual nation states," Fallon added.

"We agree Europe needs to do more: it's facing terrorism, it's facing migration, but simply duplicating or undermining NATO is the wrong way to do it," he said.

Despite the UK's planned departure from the EU, Fallon said the UK would continue to contribute to European defense as a member of NATO.

"We are leaving the European Union but we remain committed to the security of Europe and putting more troops into Estonia or Poland next year," Fallon said.

Uniting strengths

German Defense Minister Ursula von der Leyen insisted on Tuesday, however, that plans to step up defense cooperation is not a move against NATO.

"On the contrary, it's about bringing together the different strengths of European countries so that they are able to act together quickly," von der Leyen said.

NATO Secretary General Jens Stoltenberg also said there was no concerns within the alliance that an EU effort would undermine its operations.

"There is no contradiction between a strong European defense and a strong NATO; actually it reinforces each other," Stoltenberg told reporters.

"The importance is that we avoid duplication, that it is complementary."