The United Nations in Syria appealed on Tuesday for a one-month truce in the conflict to allow aid to reach hundreds of thousands of civilians in urgent need of assistance.
In a statement issued in Damascus, the UN said a humanitarian crisis was unfolding in several parts of the country to which it was not being given access.
The UN's humanitarian coordinator and top envoys in Syria called "for an immediate cessation of hostilities lasting for at least one month throughout Syria."
The measure would "enable the delivery of humanitarian aid and services, evacuation of the critically sick and wounded, and alleviation of people's suffering, to the extent possible, wherever they are," the UN said.
It went on to list some of the emergencies across Syria, where conflict has raged uninterrupted for almost seven years, killing more than 300,000 people and displacing millions.
Regime and allied forces are currently engaged in military operations against rebels and Islamist militants on several fronts, including in the northwestern province of Idlib and on the outskirts of Damascus.
On January 20, Turkish forces backing Syrian rebels launched a major operation against the Kurdish-controlled region of Afrin in the north of the country.
Large numbers of people who were displaced by last year's operations against the Islamic State group in the Raqa and Deir Ezzor regions are still in urgent need of humanitarian relief.
The UN said existing agreements on the delivery of aid were not being honoured and stressed that "if access was granted, three convoys could be dispatched each week, reaching over 700,000 people in these areas in two months."
While the fighting is abating in some parts of the country, the humanitarian crisis is still in full swing and aid groups predict a further 1.5 million people will be displaced in 2018.