Britain will not seek to prevent closer European defence co-operation following its exit from the EU, Foreign Secretary Boris Johnson has said.
Mr Johnson said the UK's interest was to have close relations with a "strong EU" following Brexit, and London would not "block or impede" steps towards further integration, including a European defence "architecture".
"If they want to do that, fine," he said, in comments which appeared to contradict Defence Secretary Sir Michael Fallon, who has insisted that the UK will "continue to oppose any idea of an EU army or EU army headquarters, which would simply undermine Nato".
Proposals under discussion in Brussels could see a new joint EU military command, as well as increased defence spending and joint development of assets such as helicopters and drones.
The move is being spearheaded by France and Germany, who insist the plan is to improve co-operation and not create the EU's own army.
Speaking at Chatham House in London, the Foreign Secretary rejected suggestions that it was in the UK's interests for the EU to fall apart, with other countries following Britain's lead in voting to leave.
And he indicated he would not oppose further EU security integration, though he stressed that the priority should be to ensure member states meet Nato's target of spending 2% of GDP on defence.
"We want a strong EU and we want a strong relationship between a strong UK and a strong EU," said Mr Johnson.
"It is no part of our agenda to seek to undermine or to be dog-in-the-mangerish about the EU.
"There's a conversation going on now about the EU's desire to build a common security and defence policy and a new architecture for that. If they want to do that, fine - obviously they should also spend 2% of their GDP on defence.
"We are not there to block or to impede further steps towards EU integration if that is what they desire. We are there to support and to build a strong, thick relationship."
Mr Johnson insisted that the June 23 vote for withdrawal from the EU should not be seen as the UK turning its back on the world, and issued a plea that Britons should not be regarded as xenophobes or populists because of it.
He acknowledged that the Brexit vote had "startled" Britain's friends around the world, but said the UK should not be "defined" by it. Rather than turning its back on the world, the post-Brexit country must be "more outward-looking and more engaged with the world than ever before," he said.
The Leave vote was not driven by "xenophobia" and the desire to leave the EU was compatible with "a generous and open mindset towards the rest of the world", insisted Mr Johnson.
"This is the year when - as we periodically do - we did something that startled our friends and rivals," said the Foreign Secretary.
"We voted to leave the EU.
"Ever since that extraordinary vote on June 23 there have been efforts to psychoanalyse the result and to impute bad motives to the British people, and there have been plenty who have been only too quick to draw comparisons with populist movements across the world."
But he rejected this as a "glib" interpretation of the referendum result, and said he counted himself among "plenty" of Leave voters who backed Brexit "not because they disliked or feared foreigners but because they believed in democracy".
"It is my passionate belief that there is no contradiction between a trust in the nation state as the key-building block of the global order and a generous and open mindset towards the rest of the world," said Mr Johnson.
"Brexit emphatically does not mean a Britain that turns in on herself. Yes, a country taking back control of its democratic institutions but not a nation hauling up the drawbridge or slamming the door.
"A nation that is now on its mettle, a nation that refuses to be defined by this decision, a country galvanised by new possibilities and a country that is politically and economically and morally fated to be more outward-looking and more engaged with the world than ever before."
Responding to Mr Johnson's comments, a Downing Street spokesman said: " We are very clear that Nato is the bedrock of our and Europe's defence.
What we have been clear about is that any EU defence and security proposals that may come forward should complement Nato and not duplicate Nato."
The spokesman stressed that no proposals had yet been tabled in Brussels for a Europe-wide defence force.
"We remain members of the EU at the moment and we have made clear we don't agree with a European defence force," he added.
Mr Johnson said it was the UK's "historic post-Brexit function" to stand up for free trade against the growing tide of protectionism around the world.
"The gossamer web of obstruction is growing thicker every year, and the political support for openness in trade is draining away across the world," he warned.
"For the first time in decades trade is no longer growing as fast as global GDP, with volumes rising by only 2.8% this year compared with an average of 5% since 1990.
"And since it is the world's poorest who will suffer most from this atrophy, it is our historic post-Brexit function - as the PM has said - to be the leading agitators for free trade.
"Again confounding those who are willing to misread Brexit by seizing the moment to campaign for openness and open markets across the globe, beginning with some of those dynamic Commonwealth economies that are already queuing up to do free trade deals."