Boris Johnson is to warn the world risks slipping back into a "brutal" era where strong men dominate and democracy is in retreat.
In his first major speech as Foreign Secretary, Mr Johnson insists the UK must retain a leadership role in world affairs after Brexit.
The Foreign Secretary makes it clear he disagrees with Donald Trump's campaign stance that America may not come to the defence of some of the Baltic States unless they make a bigger financial contribution to Nato, but is backing the US president-elect's call for members of the organisation to ease the cost burden on Washington.
Amid fears in some Nato capitals that Mr Trump is preparing to to take a softer line with Vladimir Putin, Mr Johnson is using his address to the Royal Institute of International Affairs at Chatham House to say that the West must remain tough with Russia, but be prepared to talk to Moscow.
Mr Johnson says the global liberal order needs to be protected, and points to Libya, where former prime minister David Cameron intervened militarily, as part of an "arc of instability" across the Middle East.
"We are struggling against non-state actors who view the whole concept of a global liberal order with contempt and it is precisely because of the intensity of these challenges that we need to redouble our resolve and to defend and preserve the best of the rules-based international order.
"If we fail, then we risk reverting to an older and more brutal system where the strong are free to devour the weak where might is always right and the rules and institutions we have so painstakingly built fade away into irrelevance. We cannot allow this to happen.
"We have to acknowledge that in many respects the world is not in good shape. We have the cult of the strong man, we have democracy in retreat, we have an arc of instability across the Middle East from Iraq to Syria to Libya. What is the answer of the UK, is it to cower and put the pillow over our heads? Emphatically not."
The Foreign Secretary explicitly commits Britain to the concept of collective Nato defence.
"Our resolve to fulfil our Nato obligations will be unbreakable. At the heart of this extraordinary institution. The most durable and successful defensive alliance in history lies the security guarantee contained in the North Atlantic treaty article five, that an attack on any one member 'shall be considered an attack against them all'.
"And President-elect Trump has a point, it cannot be justified that one Nato ally, America, accounts for about 70% of the alliance's defence spending while the other 27 countries manage only 30% between them. I want every Nato member to meet the agreed target of spending 2% of GDP on defence, and 20% of their defence budget on new equipment. Britain already abides by this target and I note that Nato's most exposed members - including Estonia and Poland - do so as well."
Mr Johnson urges the West to maintain a strong stance against Russia, but engage in dialogue with Mr Putin.
"Britain is prepared to be tough with Russia, but that does not mean that it is not also sensible to talk. Yes, it is Britain that insists on our resolve to enforce sanctions against Russia for their occupation of Crimea and their hand in the war in eastern Ukraine and it is Britain again that has been the firmest in denouncing Russia's part in the destruction of Aleppo.
"For all these reasons we cannot normalise relations with Russia or go back to 'business as usual'. But as I have said time and again Russia could win the acclaim of the world by halting its bombing campaign in Syria, delivering Assad to peace talks and abiding by the letter of the Minsk agreements in Ukraine and once more I will not shy away from delivering those messages face to face.
"As the Nato secretary general has pointed out, there is no contradiction between deterrence and dialogue."
Mr Johnson says, while Britain is a small island, it still has a big reach, and that will continue after Brexit.
"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.
"To those who say we are now too small, too weak, and too poor to have any influence on the world. I say there are plenty of people who do understand what this country can do and the effect it can have. Indeed, there are many people in this country who would not recognise the image of Britain - of ourselves - as seen through the eyes of others."
The Foreign Secretary says the UK's special relationship with the US will endure.