The 15 doctors serving the 300,000 people still living in eastern Aleppo urged the President to create a permanent lifeline to bring in urgently needed medical supplies.
"We have 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," said the letter.
And while there were rare celebrations in the streets, the battered enclave is still far from peaceful, with tens of thousands of families trapped by fighting, basic infrastructure severely damaged, and access to humanitarian aid limited.
The eastern part of the city has been held by rebel groups since 2012
with the recent government siege, backed by Russian air power, cutting off many supply routes.
More than 6,000 people, mainly civilians, were killed or injured in 80 consecutive days of fighting in Aleppo, according to the Syrian Observatory for Human Rights.
"What pains us most, as doctors, is choosing who will live and who will die," said the letter, which was first released with the signatures of 29 doctors, and later revised to 15.
"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."
But despite these horrors, the doctors added: "We choose to be here. We took a pledge to help those in need. "
The White House has received the letter, a senior administration official told CNN on Thursday.
"The US has repeatedly condemned indiscriminate bombing of medical facilities by the Assad regime in Aleppo and elsewhere in Syria.
"These attacks are appalling and must cease," the official continued. "We commend the bravery of medical professionals across Syria who are working every day in perilous circumstances with minimal supplies to save lives."
The official said the US government is working with the United Nations and engaging with Russia to find a diplomatic approach to reducing the violence and allowing humanitarian assistance into the city.
Dr. Hamza, a Syrian doctor in Aleppo who signed the letter and did not provide a first name, said he was shocked at the response from the White House.
"Speaking about humanitarian assistance and speaking about negotiation and diplomatic solution is very ironic while the Russian air forces are right above our heads and striking us with every weapon that any man can imagine" said Hamza. "The White House knows exactly what is happening," he said.
Hamza said the response from the Obama administration felt particularly tone deaf, given what he suspects was a chemical attack in Aleppo late Wednesday.
Supplies dangerously low
The doctors say there is an attack on a medical facility every 17 hours, meaning services in the area could be annihilated within one month if no action is taken soon.
"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 said.
"Death has seemed increasingly inescapable."
Across the city, more than 2 million people are without access to electricity, said United Nations spokesman Stephen O'Brien at a press briefing.
The little water that is available through wells and tanks is not nearly enough to sustain the population through the scorching Syrian summer, with children particularly at risk of waterborne disease, he added.
Doctors pushed to breaking point
Despite the daily atrocities, the Syrian doctors spoke of their overwhelming duty to help others -- and urged the United States to assume a similar sense of responsibility.
Some of the doctors had been visiting their families when they heard Aleppo was being besieged and rushed back to help, several on foot because the roads were too dangerous.
"Because without us even more of our friends and neighbors will die. We have a duty to remain and help," said the letter.