UN Secretary-General Ban Ki-moon attends a high-level meeting on Syria at the Security Council Chamber at the UN Headquarters in New York, Sept 21, 2016. [Photo/Xinhua]

Our world faces formidable challenges. Gulfs of mistrust divide citizens from their leaders. Extremists push people into camps of "us" and "them". The Earth assails us with rising seas and record heat. One hundred and thirty million people need life-saving assistance, tens of millions of them children and young people -- our next generation already at risk.

Yet after ten years in office, I am convinced that we have the power to end war, poverty and persecution, close the gap between rich and poor, and make rights real in people's lives. With the 17 Sustainable Development Goals, we have a new manifesto for a better future. And with the Paris Agreement on climate change, we are tackling the defining challenge of our time.

These great gains are threatened by grave security threats. Armed conflicts have grown more protracted and complex. Governance failures have destabilized many societies. Radicalization has threatened social cohesion – precisely the response that violent extremists seek and welcome. The tragic consequences are on brutal display from Yemen to Libya and Iraq, from Afghanistan to the Sahel and the Lake Chad Basin. The conflict in Syria is taking the greatest number of lives and sowing the widest instability, as the Government of Syria continues to barrel bomb neighbourhoods and powerful patrons keep feeding the war machine. Accountability for atrocious crimes such as the recent attack on a UN-Syrian Arab Red Crescent aid convoy is essential. I continue to press all those with influence to get talks started towards a long overdue political transition. The future of Syria should not rest on the fate of a single man.

In too many places, leaders are rewriting constitutions, manipulating elections, imprisoning their critics and taking other desperate steps to cling to power. Leaders must understand that holding office is a trust, granted by the people, not personal property.

The recently adopted New York Declaration on Refugees and Migrants can help us to better address the largest forced displacements of people since the Second World War. All too often, refugees and migrants face hatred, Muslims in particular. The world must speak out against political leaders and candidates who engage in the dark and dangerous political math that says you add votes by dividing people and multiplying fear.

Looking back over ten years in office, I am proud that UN Women came to life and has become a champion of gender equality and empowerment, aiming for a "50-50 planet". I am proud to call myself a feminist. Yet we must do far more to end deep-seated discrimination and chronic violence against women and to advance their participation in decision-making. I have also strongly defended the rights of all people, regardless of ethnicity, religion or sexual orientation, as well as the freedoms of civil society and independent media to play their essential roles.

Continued progress will require new heights of solidarity – and continued efforts to strengthen peace operations and adapt the United Nations for 21st-century challenges. Member States have still not agreed on a formula for reform of the Security Council -- a continuing risk to its effectiveness and legitimacy. Far too often, I have seen good ideas and widely-supported proposals blocked in the Council, General Assembly and other bodies in the search for consensus. Consensus should not be confused with unanimity. Doing so ends up giving a few countries or even just one State disproportionate power, holding the world hostage on important issues.

I have visited almost all the UN's Member States over the past decade. What I have seen, more than Government buildings and global landmarks, is the remarkable power of people. A perfect world may be on the far horizon. But a route to a better world, a safer world, a more just world, is in each and every one of us. Ten years on, I know that working together, working united, we can get there.

The author is Secretary-General of the United Nations