The focus of the plight of the Syrian people has shifted away from the apex of horror that was the suffering caused by the siege of eastern Aleppo. Now we must not let the lives of millions of people in desperate need across Syria slip from the world’s conscience.

Millions displaced and 500,000 dead – will new peace talks end Syria’s agony? Read more

In 2016 we saw devastation and suffering in Syria at levels that defied human understanding. We witnessed people dying of starvation, children pulled from the rubble of their bombed homes, and bombs and mortars raining down on schools, health clinics, markets. We saw essential services such as electricity and water disrupted for millions of people. We saw buses that were intended to evacuate civilians being set on fire. We saw towns besieged, bombed and then emptied. And we saw the relentless demolition of eastern Aleppo.

Now, far from being on the wane, the scale and complexity of humanitarian and protection needs inside Syria are unprecedented. Six years after the onset of brutal violence, 13.5 million people cannot access the basics they need to survive, let alone to thrive. Just less than half of these people are internally displaced; many have taken shelter with host families who are themselves now struggling to survive. And we should not forget that there are 430,000 Palestinian refugees in Syria, 95% of whom need humanitarian assistance.

In a barbaric war tactic, fighting parties are still besieging more than 600,000 people in towns across the country. Few of us can imagine the horrors of being besieged, with all freedom of movement curtailed and no access to the very basics of life: food, schooling, medical supplies, clean water and warm clothes. Almost half of these people are children who have known little else but conflict, loss and fear throughout their short lives. A lost generation.

Facebook Twitter Pinterest Destruction in eastern Aleppo after government forces took control of the rebel-held area. Photograph: George Ourfalian/AFP/Getty Images

In addition, an estimated 4 million people live in areas considered hard to reach for the UN and its partners. This is down to a variety of reasons, including ongoing fighting, insecurity and continual blocks on aid convoys filled with life-saving assistance.

Let’s be clear: the UN and its partners do have the capacity to deliver to hundreds of thousands of people in these besieged and hard-to-reach areas every month. We are ready to move.

We had hoped the ceasefire would lead to an improvement in humanitarian access. However, while it has provided many people with a rare moment of respite, we are still blocked at every turn in our efforts to reach people in need, particularly in besieged and hard-to-reach areas. The central and local authorities continue to refuse approval for aid deliveries, disagree over access routes and violate agreed procedures at checkpoints.

On the ground, this means people continue to go hungry, fail to receive the medical care they need, cannot educate their children and are forced to suffer needlessly.

The need for a political solution to end this horrendous chapter in Syria’s history is as urgent and profound as ever

Despite the herculean obstacles we face, the UN and its local and international partners are doing all they can to reach those in need. Together, we continue to support millions of people across Syria every month due to the brave and brilliant work of so many people – humanitarian volunteers and professionals working with NGOs, civil society groups, the Syrian Arab Red Crescent and UN agencies.

We are saving and rebuilding lives in Syria daily. In 2016, the food sector covered about 6 million people a month; the health sector delivered more than 14 million health supplies and treatments. We covered 3 million children with nutrition support and provided the basic essentials of life for more than 4 million people. We did this in line with the humanitarian principles of impartiality, neutrality and independence, through methods including regular programmes, cross-line convoys, cross-border shipments and air operations.

Still, these numbers fall short of the 13.5 million people in need across the country. We have identified their key humanitarian requirements for 2017: $3.4bn (£2.7bn) is needed not only to save and protect lives, but also to help families and communities rebuild their lives and livelihoods, wherever possible, despite the ongoing insecurity.

However, to do this and reach everyone, we need unconditional, unimpeded and sustained access to every single person in need in Syria, no matter where they are or what side of the conflict (if any) they are on. We also call for freedom of movement for all people so they can access essential services, livelihoods and the very basics of life for their families.

This crisis continues to test our common humanity and our commitment to protecting people in great need. The need for a political solution to bring an end to this horrendous chapter in Syria’s history is as urgent and profound as ever.

In the meantime, we cannot fall into complacency, avert our gaze or hold up our hands in exasperation. Too many Syrians, both inside the country and those across borders who may one day want to come home, rely on us so they can make ends meet.

Syrians, Syrian civil society and the entire humanitarian community have not forgotten this crisis.

We will not forget. We call on the rest of the world to do the same: this is the time to intensify our support for the Syrian people and reignite their chance of hope.