Geneva (AFP) - The UN's humanitarian chief said Monday he was "pained" that aid convoys had not deployed to eastern Aleppo, as a ceasefire in Syria teetered on the brink of collapse.
The delivery of desperately needed supplies to Aleppo's rebel-held east and besieged areas across the country was a key component of the truce agreed by the United States and Russia that came into force last week.
But UN trucks carrying life-saving supplies destined for Aleppo have been stuck in a buffer zone between the Turkish and Syrian borders since early last week.
"I am pained and disappointed that a United Nations convoy has yet to cross into Syria from Turkey, and safely reach eastern Aleppo, where up to 275,000 people remain trapped without food, water, proper shelter or medical care," said a statement from Stephen O'Brien, who heads the UN's humanitarian office (OCHA).
The US-Russia deal included specific measures aimed at getting aid into eastern Aleppo.
The pact called for Syrian troops to withdraw from the Castello Road supply route into the city, which regime forces seized in early July, cutting off aid to Aleppo's east.
The UN has said its trucks would not roll until Washington and Moscow signalled that the Castello Road was clear and safe.
Addressing the UN rights council on Monday, the head of the United Nations Commission of Inquiry for Syria, Paulo Pinheiro, sounded a further call for "unimpeded, sustained and rapid humanitarian access to all those in need."
"Roadblocks made of red tape are just as effective as roadblocks made of weapons of war," he told the council.
Meanwhile, fears mounted Monday that the fragile truce was failing.
Regime ally Russia and the US, which backs some opposition groups, have blamed each other for cracks in the ceasefire.
Moscow and Damascus have blasted Washington over airstrikes that killed scores of Syrian soldiers on Saturday in Deir Ezzor, which is partly held by the Islamic State group.
The Pentagon has conceded that Syrian troops may have been hit in the raid targeting IS.
Syria's envoy to the UN in Geneva, Hussam Edin Aala, charged in the rights council that the US strikes were "planned and deliberate."