UNITED NATIONS: Weekly 48-hour humanitarian pauses are urgently needed in Syria's Aleppo city where fighting has left over a quarter of a million people trapped and in desperate need of aid, the UN humanitarian chief said on Monday.

Stephen O'Brien told the Security Council that he could not stress enough "how critical the situation is" in the eastern part of Aleppo, which risks becoming the largest besieged area in the country. Food supplies are expected to run out in mid-August and many medical facilities continue to be attacked, he said.

"This is medieval and shameful," O'Brien said. "We must not allow this to happen. But the clock is ticking."

Britain's UN Ambassador Matthew Rycroft said he received an email Monday morning from a doctor at Aleppo Children's Hospital saying "if nothing is done we are surely facing death."

"Eastern Aleppo City is now encircled by the regime," said Rycroft. "The Castello road, a vital route for food, medicine and supplies, is cut off. ... Yet another humanitarian catastrophe awaits."

Syrian government forces and their allies cut the Castello road, the main link to rebel-held parts of the country, on July 17 — laying siege to opposition-held parts of Aleppo. The country's largest city and former commercial center has been contested since July 2012 and Aleppo residents have been reporting shortages of food in rebel-held parts of the city because of the siege.

Russia's UN Ambassador Vitaly Churkin said the road was being used to deliver aid to "terrorists." U.S. Ambassador Samantha power demanded that the road be reopened.

O'Brien said his call for 48-hour pauses must be backed by the Security Council, the UN's most powerful body.

Japan's UN Ambassador Koro Bessho, the current council president, said there was "overwhelming support" from the 15 members but wouldn't say whether a resolution is planned.

The United Nations says there are nearly half a million people in besieged areas in Syria and an estimated 4.5 million Syrians are in so-called "hard-to-reach" areas.

The Syrian military declared a unilateral, three-day cease-fire for the entire country on July 6, coinciding with the start of the Muslim Eid al-Fitr holiday, but it didn't hold. The previous high-profile "cessation of hostilities" brokered by the United States and Russia and declared on Feb. 27, sharply reduced violence in much of the country. But it collapsed in April with a government offensive in the northern province of Aleppo against a coalition of insurgent groups.

O'Brien demanded the restoration and consolidation of the cessation of hostilities, the lifting of all sieges in the country, and access throughout Syria for humanitarian workers to help the sick and needy.

The humanitarian chief said he was "alarmed" at the reported deteriorating of humanitarian conditions in four towns — Madaya, Zabadani, Foua, and Kafraya — where over 62,000 people are besieged. He warned that pictures of starving children are "highly likely" in these towns unless immediate and unconditional aid deliveries and urgent medical evacuations are allowed.