Smoke rises from Ramousah as seen from a rebel-held area of Aleppo, Syria, August 22, 2016. (REUTERS/File Photo)

UNITED NATIONS, Aug. 22 (Xinhua) -- Stephen O'Brien, the UN under-secretary-general for humanitarian affairs, on Monday reiterated his call for a 48-hour ceasefire in Syria's northern city of Aleppo, saying that the United Nations is ready to send humanitarian assistance to the people in the city.

O'Brien, in his briefing to the UN Security Council, stressed that anything shorter than 48 hours would not allow for a meaningful response.

"The UN is ready to move 70 trucks of assistance into eastern Aleppo as soon as we receive the necessary security assurances," said O'Brien, who is also the UN emergency relief coordinator. "Once we have the green light, we can move assistance within 48 to 72 hours."

While noting progress in reaching besieged and hard-to-reach areas since the beginning of the year, O'Brien deplored that we now appear to be in reverse gear.

In August, the United Nations was denied access to more than 50 percent of requested beneficiaries. Moreover, active conflict and insecurity, as well as delays in getting facilitation required to move convoys have been limiting factors. As a result, no inter-agency convoys have moved in August.

Calling Syria "the greatest crisis of our time," O'Brien stressed the Security Council cannot look the other way and called on the 15-nation council to ensure the full implementation of its resolutions.

He said that what is happening in Aleppo and throughout Syria is "an outrage against every moral fibre in our being as human beings" and called on council members to put differences aside and stop this "humanitarian shame."

At least 51 people were killed as a result of rebels' shelling and airstrikes in Aleppo, reports said early this month.

At least 45 civilians were killed in Aleppo and to the west of the city, and another 22 died in neighbouring Idlib province, reports said last week.

Aleppo, Syria's largest province and once a thriving economic metropolis, has witnessed intensified violent battles lately as both the Syrian government troops and the opposition fighters have stepped up their game in the hope of achieving more gains in that key province.