We met a year ago, on the brink of a global crisis, and, as national leaders spoke in turn at this podium, the full scale of the danger became clear: a threat not just to jobs, businesses and life savings but - with the imminent risk of failure of the world’s banking system - the prospect of entire countries failing, as nations across Eastern Europe, Asia and Latin America struggled to access credit.

The crisis demanded global action.

As never before, the fate of every country rested on the actions of all. And as the fear of the unthinkable took hold, we reached a clear choice: to fail separately or to succeed together.

At the G20 in Washington and again in London, we made our choice. Governments came together to begin the fight back against the global recession; we acted in concert, recognising:

 that national interests could be protected only by serving the common interest;
 that in this new global age the economy is indivisible and recession anywhere can threaten prosperity everywhere;
 that for growth to be sustained it has to be shared;
 and that global challenges can only be mastered through global solutions.

So today we can draw strength from the unprecedented unity that has defined the past year - but we cannot be complacent. For while it may seem strange to say so after a time of such intense global action, our world is entering a six-month period which may prove even more testing for international cooperation.

We face five urgent challenges that demand momentous decisions - decisions that I would argue are epoch-making - on:

 climate change,
 nuclear proliferation,
 poverty and
 shared prosperity

Once again we are at a point of no return. And just as the collapse of the banks focused our minds a year ago, so we must now grasp this next set of issues.

If we do not reach a deal at Copenhagen, if we miss this opportunity to protect our planet, we cannot hope for a second chance some time in the future. There will be no retrospective global agreement to undo the damage we will have caused. This is the moment, now, to limit and reverse the climate change we are inflicting on future generations. Not later, at another conference, in another decade, after we have lost ten years to inaction and delay.

And if in Afghanistan we give way to the insurgency, Al Qaeda and other terrorist groups will return and from that sanctuary once again plot, train for, and launch attacks on the rest of the world.

There can be no chance of a nuclear-free world, if we allow Iran to develop nuclear weapons and in doing so set off a new arms race.

There can be no global compact for jobs and growth if we choke off recovery by failing to follow through on the co-ordinated global fiscal expansion we agreed and put in place.

And if we do not act together to fight preventable illness, there can be no plan to save tomorrow the 12,000 children who are dying in Africa today and every day.

So I say we need world agreement.

First, on climate change.

Despite the promises we have all made, the road to a successful outcome on climate change in Copenhagen is not assured. Why? Above all, because a robust and long term climate change deal requires money. If the poorest and most vulnerable are going to be able to adapt; if the emerging economies are going to embark on low carbon development paths; if the forest nations are going to slow and stop deforestation - then the richer countries must contribute financially.

That is why I have proposed a new approach to financing our action against climate change, which will provide substantially increased, additional and predictable flows, from both public and private sectors, of around $100bn a year by 2020. We must make progress on this in the coming days.

A post-2012 agreement on climate change at Copenhagen is the next great test of our global cooperation. Each of us has a duty of leadership to make it happen. We must build on our discussions at Secretary-General Ban’s meeting here this week. And I have said I will go to Copenhagen to conclude the deal. This is too important an agreement - for the global economy, and for the future of every nation represented here - to leave to our official negotiators. So I urge my fellow leaders to commit themselves to going to Copenhagen too.

Second - terrorism.

A safer Afghanistan means a safer world. But none of us can be safe if we walk away from that country-or from our common mission and resolve.

NATO and its partners from Australia to Japan must agree new ways to implement our strategy - ensuring that Afghanistan, its army, its police and its people assume greater responsibility for the security of their own country.

So too must we unite against every source of terror and injustice in our world.

It shames us all:

 that the people of Somalia and Sudan are still subject to the most terrible violence;
 that Israel and Palestine have still not found a way to live side by side in security and peace;
 and that for the people of Burma, their elected leader is subjected to a show trial and decades of incarceration.

There is more we can do; there is more we must do. And we must carry forward our efforts to take a more strategic, coherent and effective approach to peacekeeping and peacebuilding.

Third - nuclear proliferation.

Once there were five nuclear-armed powers. Now there are nine, with the real and present danger that more will soon follow. And the risk is not just state aggression, but the acquisition of nuclear weapons by terrorists.

So we are at a moment of danger when decades of preventing proliferation could be overturned by damaging rise in proliferation.

If we are serious about the ambition of a nuclear free world we will need statesmanship, not brinkmanship.

Tomorrow’s Security Council Resolution will be vital as we move forwards towards next year’s global nuclear security summit in April and the Review Conference in May.

My proposal is a grand global bargain between nuclear weapon and non nuclear weapons states.

And there are three elements to it where careful and sober international leadership is essential and in which Britain will play its part on the responsibilities on non nuclear states, on the rights of non nuclear states, and on the responsibilities of nuclear weapon states.

First, let there by no ambiguity: Iran and North Korea must know that the world will be even tougher on proliferation and we are ready to consider further sanctions. Britain will insist that the onus on non nuclear states is that in future it is for them to prove they are not developing nuclear weapons.

Second, Britain will offer civil nuclear power to non nuclear states ready to renounce any plans for nuclear weapons: helping non-nuclear states acquire what President Eisenhower so memorably called “atoms for peace.” With others we will be prepared to sponsor a Uranium bank outside these countries to help them access civil nuclear power. And Britain is ready to launch a new nuclear centre of excellence to help develop an economic low-carbon proliferation-resistant nuclear fuel cycle.

Third, all nuclear weapons states must play their part in reducing nuclear weapons as part of an agreement by non nuclear states to renounce them. This is exactly what the Non Proliferation Treaty intended. In line with maintaining our nuclear deterrent I have asked our national security committee to report to me on the potential future reduction of our nuclear weapon submarines from four to three.

Fourth, while economic cooperation has stabilised the international banking system and forged a foundation for the resumption of economic growth, recovery is neither entrenched nor irreversible.

The great lesson of the last year is that only bold and global action prevented a recession becoming a depression. We have delivered a co-ordinated fiscal and monetary response that the ILO estimates has saved 7 to 11 million jobs across the world.

So at Pittsburgh tomorrow, we must cement a global compact for jobs and growth - a compact to bring unemployment down and bring rising prosperity across the globe:

 maximising the impact of the stimulus measures we have agreed, with proper planning of exit strategies, to make sure the recovery does not falter; that we do not turn off the life support for our economy prematurely;
 facilitating agreement setting clear objectives on how each of us can best contribute to worldwide growth in the future;
 and ensuring that such growth is balanced and sustainable.

We need strong economic co-ordination now as we navigate the uncertainties of recovery. I therefore propose that we launch the compact by agreeing that we are committed to high levels of growth on a sustainable and balanced basis.

This must be backed up by comprehensive reform of the financial sector, including international principles on bonuses. And we must strengthen our targeting of tax havens with, from next March, real sanctions against those jurisdictions which fail to meet global standards.

But the voice of Africa will have to be heard and heeded to bring recovery in areas devastated by the events of the past year and to assure that we do not put the millennium development goals beyond reach as a result of a wider failure of global responsibility.

In London, the G20 agreed measures to result in $50 billion for poor countries to help them weather the crisis. Because of London, the IMF can lend $8 billion instead of $2 billion over this year and next. This is already helping Kenya and Tanzania to increase government spending in response to the crisis.

For amid all the challenges we face, we must remember a promise we made 10 years ago. And this is the fifth and final imperative: to achieve a vision for 2015 we are now in danger of betraying. On present trends it will take not five years as we pledged and not even 50 years, but more than 100 years to deliver on some of the Millennium Development Goals.

The unyielding, grinding, soul-destroying, so often lethal poverty I saw in Africa convinced me that unless empowerment through trade justice is matched by empowerment through free education and free health care, then this generation in sub-Saharan Africa will not have the opportunity to rise out of poverty and will never be fully free.

The greatest of injustices demands the boldest of actions.

Today - at this United Nations General Assembly - we will see the beginnings of universal free health care in Africa and Asia as Burundi, Sierra Leone, Malawi, Nepal, Liberia and Ghana all make major announcements that extend free care and abolish fees.

As a result of these actions, more than 10 million more people in Africa and Asia will now have access to free health services. Ten million who will now for the first time get the treatment they need without being turned away or fearing how they will pay.

I urge you all to match the leadership of these countries with your own support. And I commit the UK to doing so.

Let us remember how in 1945 nations facing a multiplicity of challenges summoned up the energy and vision not just to rebuild from the rubble and ruin of war, but to establish a new international order for shared security and progress.

The same principles must now inspire new and better, more representative, and more effective ways of working together.

And as we learn from the experience of turning common purpose into common action in this our shared global society, so we must forge a progressive multilateralism that depends on us finding within ourselves and together the qualities of moral courage and leadership that for our time and generation can make the world new again-and for the first time in human history, create a truly global society.