The city has come under intense and sustained aerial bombardment by the Syrian government and Russian forces since a truce brokered by Washington and Moscow collapsed last month.
The US, however, has now cut off contacts with Russia on a Syrian truce, giving up hopes of restoring a ceasefire.
As a Russian-Syrian aerial bombing campaign intensified, with its focus on destroying hospitals in rebel-held areas, Ban Ki-moon described the latest breakdown in talks as “heartbreaking and troubling.”
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The official, who was in Parliament for the signing of the COP21 climate deal, “strongly urged” the two sides to return to the negotiating table so that humanitarian aid might get through to those trapped in Aleppo.
The official was due to travel to Brussels later on Tuesday to attend a major international conference on Afghanistan where, he said, he hoped to speak to John Kerry, the U.S secretary of state, and “high ranking” Russian officials about the current situation in Syria.
He said, “There is an urgent need to get humanitarian aid through to those who need it most. We need to show some global responsibility.”
Suspending the talks, Washington accused Moscow of having "failed to live up" to its commitments under the recent truce deal.
Hundreds of people, including children, have died since government forces launched an offensive to take full control of Aleppo on 22 September.
The suspension of talks comes after EU foreign affairs chief Federica Mogherini and European humanitarian aid and crisis management Commissioner Christos Stylianides earlier this week outlined an emergency humanitarian initiative for Aleppo aimed at allowing humanitarian organisations to do their work and civilians to be rescued and protected.
A Commission source said the initiative, conducted in cooperation with the UN, consists of two main elements.
He said, “First, it aims at facilitating the urgent delivery of basic life-saving assistance to civilians in east Aleppo covering medical, water and food needs.
“An inter-aid agency convoy stands ready to move from west to east Aleppo drawing on prepositioned stocks made possible also through EU first line response funding. This convoy can deliver aid to a maximum of 130,000 people.
“Second, in parallel and simultaneously, the initiative aims at ensuring the medical evacuations of wounded and sick from eastern Aleppo in urgent need of medical care, with a focus on women, children and the elderly.”
The EU has called on all parties to “unite on this humanitarian initiative for Aleppo for the sake of humanity and the political future of Syria.”
The EU is also mobilising a €25m emergency aid package to support and scale up the first line response of its humanitarian partners to cover urgent medical, water and sanitation, and food assistance in Aleppo and in other priority areas across the country.