WASHINGTON — (CNN) A senior UN humanitarian affairs official has condemned in the strongest terms the international community’s response to the crisis in Aleppo, where he says war crimes are being committed.

Undersecretary-general for Humanitarian Affairs and Emergency Relief Coordinator Stephen O’Brien called the civil war the “ultimate humanitarian shame that is Syria today, and in east Aleppo in particular.”

In the uncompromising speech, O’Brien lambasted the inaction — “be it through unwillingness or inability” — of the international community to intervene in the crisis, which has only escalated in violence since the disintegration of a ceasefire last week.

Repeating the accusations of UN Secretary General Ban Ki-moon, O’Brien said that the destruction of medical facilities in rebel-held eastern Aleppo and the use of “ever more destructive weapons” means that those using them “know they are committing war crimes.”

He said that the residents of the beleaguered city, particularly those in the eastern part of the city, including 100,000 children, are “being subjected to deprivation, disease and death in increasing numbers and with increasing ferocity.”

“Let me be clear, east Aleppo this minute is not at the edge of the precipice, it is well into its terrible descent into the pitiless and merciless abyss of a humanitarian catastrophe unlike any we have witnessed in Syria, with no access by the UN since 7 July; and the health sector in east Aleppo is reportedly on the very verge of total collapse.”

He said that to engage in “political grandstanding” or to ignore “the horror unfolding before our eyes” would leave the Security Council “on the wrong side of history.”

The impassioned speech comes after a week of intense bombardment of the beleaguered city, which the Assad regime is preparing to take.

An estimated 10,000 Syrian-led ground troops have gathered in advance of what is believed to perhaps be a final ground assault over the coming days by Syrian government forces against rebels holding the key city, in what one US official described as an unprecedented degree of firepower to be unleashed on the besieged area.

The US is looking at holding Russia accountable for the brutal assault on rebel-held areas of Aleppo this week, some of the worst violence since the start of the five-year war. Some US officials are already suggesting war crimes have been committed.

After speaking for the second time in 24 hours with Russian Foreign Minister Sergei Lavrov, US Secretary of State Jon Kerry told an audience at the Washington Ideas Festival that the US is “on the verge of suspending the discussion” with Russia, which was aimed a brokering a ceasefire that would have grounded Syrian aerial attacks on the city and paved the way for greater US-Russian cooperation on attacking terror groups who have taken hold during the civil war.

“It’s irrational in the context of the kind of bombing taking place to be sitting there and trying to take things seriously,” Kerry said, calling the assault on Aleppo “inexcusable” and “beyond the pale.”