In the letter 15 doctors from Aleppo have warned the situation would be desperate for civilians if regime forces re-impose a siege
Syrian doctors in opposition districts of Aleppo have accused the United States of inaction in the face of repeated atrocities in the devastated city.
In a heart-wrenching letter addressed to US President Barack Obama, 15 of the 35 doctors in eastern neighbourhoods of Syria's second city warned the situation would be desperate for civilians if regime forces re-impose a siege.
On Saturday, rebels and allied jihadists broke a three-week government encirclement that had left residents of eastern Aleppo reeling from skyrocketing prices and food shortages.
But the pediatricians, surgeons, and other physicians who signed the letter said the situation remained dire.
"Unless a permanent lifeline to Aleppo is opened it will be only a matter of time until we are again surrounded by regime troops, hunger takes hold and hospitals' supplies run completely dry."
The letter lambasts the US, saying it had seen "no effort on behalf of the United States to lift the siege or even use its influence to push the parties to protect civilians."
"We do not need tears or sympathy or even prayers, we need your action. Prove that you are the friend of Syrians."
The World Health Organization said Syria was the most dangerous place for health care workers to operate last year, with 135 attacks on health facilities and workers in 2015.
An estimated 250,000 people still live in the rebel-held eastern parts, with around 1.2 million in the government-controlled west.
Rebels and regime forces are amassing fighters around Aleppo ahead of what is likely to be a protracted battle for the northern city, whose hospitals and other civilian infrastructure have been ravaged by violence since mid-2012.
In late July, four makeshift hospitals and a blood bank in Aleppo city were hit by air raids in a single day.
Many of the signatories to the letter worked at those hospitals, where medicine is scarce and sandbags line the entrances.
"What pains us most, as doctors, is choosing who will live and who will die," the doctors wrote.
"Young children are sometimes brought into our emergency rooms so badly injured that we have to prioritise those with better chances, or simply don't have the equipment to help them."
The doctors lamented that for five years, they had "borne witness as countless patients, friends and colleagues suffered violent, tormented deaths."
One attack two weeks ago left four newborn babies dead after the force of the blast cut off the oxygen supply to their incubator.
"Gasping for air, their lives ended before they had really begun. "