UN Secretary General Antonio Guterres has urged the Security Council to authorise a new passage point on the Turkish border for humanitarian aid to reach north-east Syria, where medical supplies are running short.
The recommendation came in a report issued on Friday to council members.
Western members of the Security Council asked Mr Guterres in early January to provide new options after the council drastically reduced the number of border crossings authorised.
The western powers had specifically asked for alternatives to compensate for the closing of Al Yarubiyah transit point on Syria's border with Iraq.
"Several options can be made available but from a security and logistical perspective, in the current context, the Tal Abiyad border crossing would constitute the most feasible alternative to Al Yarubiyah border crossing," Mr Guterres said in his report.
Tal Abiyad, which can handle the logistics of a major aid operation, is controlled on the Syrian side by armed groups.
Mr Guterres said two other passage points on the Iraqi border, Al Walid and Fishkabur, both under Kurdish control, were studied but found to lack logistical capacity.
The Syrian government had suggested another Iraqi border passage at Abu Kamal, but it was found to have logistical and security problems.
Since Al Yarubiyah closed, only two passage points remain on the Turkish border for food and other aid.
Considerable medical assistance had passed through Al Yarubiyah. International aid, mainly food, has also been funneled through Damascus.
But last year not one medical convoy for the north-east passed through the Syrian capital, the report said.
"An estimated 1.9 million people are assessed to be in need of humanitarian assistance in north-east Syria, the vast majority of whom – 1.34 million people – are in areas not under government control," Mr Guterres said.
"Medical stocks are expected to run out in the coming months."
The Security Council on Thursday is to take up the report in a monthly meeting devoted to the Syrian humanitarian crisis.
UN High Commissioner for Refugees Filippo Grandi supported previous calls for a cessation of hostilities on Sunday, and appealed for urgent action to allow people trapped in the conflict to move to safety.
“We need an end to the fighting and access to safety to preserve lives,” Mr Grandi said. “The UN Secretary General has appealed for parties to the conflict to respect the rules of war.
"Every day that passes, that call is more urgent.
"Thousands of innocent people cannot pay the price of a divided international community whose inability to find a solution to this crisis is going to be a grave stain on our collective international conscience.
“As in the past, in moments of crisis, I am also appealing for neighbouring countries, including Turkey, to broaden admissions, so that those most in danger can reach safety, even knowing that capacities and public support are already strained.
“For these countries already hosting 5.6 million refugees, of whom 3.6 million are in Turkey, international support must be sustained and stepped up.”