The United Nations' Humanitarian Coordinator in Syria has expressed frustration at the failure of world leaders to put aside political differences to allow aid to enter besieged areas.
Intense bombardments in the rebel-held district of Eastern Ghouta near Damascus blocked vital deliveries on Monday, with more than a quarter of the trucks carrying food being forced to leave after the suburb came under attack in the worst day of violence since a UN Security Council had demanded a 30-day ceasefire last month.
Panos Moumtzis told The National ahead of a Security Council meeting on Wednesday that "out of the 46 convoys that managed to enter Ghouta only 32 offloaded, there was shelling and insecurity so a total of 14 trucks came back full without managing to offload".
The Syrian conflict is now entering its eighth year. Hundreds of thousands have been killed, clashes are fierce in rebel-held areas and the regime of President Bashar Al Assad has again been accused in recent weeks of using chemical weapons in his push to reclaim territory.
The vast majority inside of Eastern Ghouta are "really suffering", Mr Moumtzis said. Air strikes, artillery and rocket fire have killed more than 800 civilians and devastated residential areas since regime forces began an assault on February 18.
"On our side we say enough is enough. It's time to apply the Security Council resolution to allow us to bring in assistance at all locations and to move the process of peace and coexistence," he said, referring to the UN's call for a ceasefire.
Residents have lived under government siege since 2013 in Eastern Ghouta, facing severe shortages of food and medicines even before the latest offensive began.
Mr Moumtzis called for aid convoys to have immediate access to the main town of Douma to complete the delivery of humanitarian supplies and to allow those that need medical assistance to leave. "There's been no evacuations, there is a list of over 1,000 people that need to be evacuated and to be taken to hospitals but haven't been able to," he said.
"It creates huge frustration on our side because we are just down the road from Eastern Ghouta, it's a matter of 20 minutes to half an hour drive, where we can bring everything that is needed to help people who are otherwise dying every day."
While the UN has been criticised over Syria, Mr Moutzis said progress "depends on the political will of the parties" involved. Russia, Mr Assad's main ally, last week announced a five-hour daily "humanitarian pause" during which it said it would guarantee safe passage to civilians wishing to flee the enclave, but few are thought to have been able to.
Russia's air force intervened in Syria in 2015 on behalf of the Assad regime, helping his troops retake key cities.
"Five hours is hugely insufficient for trucks to enter Ghouta - more time is needed, the biggest frustration is that Russia voted for 30-day ceasefire, but it hasn't been applied," Mr Moumtzis said.
Instead, civilians dug deeper into their makeshift shelters on Tuesday. Many have stayed in apartment basements since the assault began.
"We feel as humanitarians there is a failure of international diplomacy, a failure of humanitarian diplomacy, the ability of the UN Security Council and us as an international community to intervene and bring an end to people's suffering," Mr Moumtzis said.
Having worked in conflict zones such as Iraq, Kenya, Rwanda and Ivory Coast and last year serving as UN Humanitarian Coordinator for Libya, Mr Moumtzis said: "It is heart breaking every morning to look at the pics of dead bodies of Syrian children, the extreme suffering that is beyond words to describe.
"People ask us why is the world failing us? Why is there no robust action? It feels as though no amount of suffering, killing, displacement, news is able to mobilise public opinion" to stop the war.
The latest attempt at peace will be in Astana next week where foreign ministers of regime allies Iran and Russia and rebel backer Turkey will meet. Repeated rounds of parallel UN-brokered talks have failed to make a breakthrough.