The Syrian Observatory for Human Rights said they were killed and dozens of people wounded when 10 Russian raids hit the city and its outskirts.
The letter went on to describe how the doctors have faced death on a daily basis for the last five years as the global community did little to protect them.
Aleppo, which has been beset by constant violence since 2012, and the site of unspeakable suffering from air strikes, ground fighting, and even chemical weapons attacks, has become a humanitarian nightmare.
The doctors said they do not need tears, sympathy or prayers, but to be free from bombings and worldwide action to prevent any future sieges. "Prove that you are friends of Syrians".
An administration official confirmed that the White House had received the letter.
A few days ago, a humanitarian corridor was opened to allow residents to leave Aleppo.
"We commend the bravery of medical professionals across Syria who are working every day in perilous circumstances with minimal supplies to save lives", she said.
During yesterday's briefing, United Nations officials also criticised Russia's proposed ceasefire of three hours a day, calling for a break of up to 48 hours instead. But the United States said that was inadequate.
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He had been under the spotlight for at least a year, as authorities believed he was a threat because he could help terror groups. Canadian Public Safety Minister Ralph Goodale said that in some circumstances peace bonds may not be the most effective tool.
Further, a Syrian rescue worker and opposition activists said on Thursday that a Syrian government air strike on opposition-held Zabadieh neighbourhood in Aleppo killed at least two people in what was alleged to have been a chlorine gas attack.
"It has been two years and more since these [Syrian opposition] groups started launching heinous assaults using chemical weapons and other banned materials against unarmed civilians in the besieged Kurdish neighbourhood of Sheikh Maqsoud in Aleppo", the YPG leadership said.
"It's really not for me to assess who did it and whether it actually took place, although there is a lot of evidence that it actually did take place", de Mistura told reporters on Thursday. On the other hand, Kurdish officials told ARA News they expect a long war to take place in Syria. Whether we live or die seems to be dependent on the ebbs and flows of the battlefield.
The letter lambasts the USA, 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". But we now face death from all around. Recent offers of evacuation from the regime and Russian Federation have sounded like thinly-veiled threats to residents - flee now or face annihilation.
A shortage of well-supplied hospitals has resulted in countless deaths that might have been prevented had the mortally wounded been able to seek medical treatment - a shortage of doctors, many of whom have either been killed or fled Aleppo since the fighting erupted, has made the situation even more dire. The doctors are quite afraid that the attack on medical facilities will wipe out medical services in Aleppo in a month if they continue at the same rate.
"Young children are sometimes brought into our emergency rooms so badly injured that we have to prioritize those with better chances, or simply don't have the equipment to help them".