Beirut (AFP) - The Syrian army's advances against rebels in east Aleppo have sparked international concern, but the world appears powerless to prevent the symbolic city from being recaptured by the government.
- Is east Aleppo's fall inevitable? -
Many experts and observers now think so.
"At this point, operationally, there's very little you can do to avert the fall of Aleppo," said Emile Hokayem, a senior fellow at the International Institute for Strategic Studies.
"You can't send weaponry in any more, all the supply roads are cut, and you won't intervene from the air because of the costs and the risks," he told AFP.
Syrian soldiers, backed by Iranian and Russian forces and Lebanon's Shiite Hezbollah militia, renewed an operation to retake east Aleppo last week.
The city has been divided since mid-2012, when rebels seized the eastern neighbourhoods a year into the uprising against President Bashar al-Assad.
After seven days of ferocious bombardment, the army has advanced quickly, seeking to slice up the rebel-held neighbourhoods where 250,000 people live.
US Pentagon officials decline to be drawn on how soon the rebels might collapse, having suggested months earlier that the city's east was on the verge of being recaptured.
The "resilience" of the rebels and the population, despite a four-month government siege, appears to have surprised them.
And they see the government's targeting of hospitals and civilian infrastructure as a reflection of its military weakness on the ground.
Even if the army effectively seizes east Aleppo, "that doesn't mean the pacification of east Aleppo", Hokayem said.
There would continue to be "lots of pockets of resistance", he added.
- Why no Western intervention? -
Despite expressions of outrage, there has been little sign of intervention from the international community, which has behaved as "a powerless bystander", said Karim Bitar, a researcher at the Institute for International and Strategic Affairs.
Despite opposing Assad's government, the West now appears impotent in the face of its advances.
"There was a time to do something about Aleppo... but now it's too late," added Hokayem.
"The key actors and key governments keep delaying the difficult decisions until there are no options left," he said.
Hokayem said backers of the opposition had misjudged how important Russia's decision to intervene militarily last year would prove in bolstering the regime.
Washington is now paralysed by the transition to president-elect Donald Trump's incoming administration.
"In the absence of a leading American role, the French or the Brits can't do much and won't do much," said Hokayem.
- Does the US care about Aleppo? -
For US military officials, the fall of east Aleppo is regarded as a non-event, with little operational consequence for them.
They say their sole focus in Syria is the fight against the Islamic State group, the only military task to which President Barack Obama has committed troops.
With just weeks before he leaves the White House, there is little sign that Obama will change his policy on Syria now.
And a Trump administration is likely to pursue a policy significantly less hostile to Assad's government and its backer Moscow.
"Indeed, discussions on Syria policy between Moscow and Trump have already begun," according to Daniel Byman, a senior fellow at the Brookings Institution think tank.
Meanwhile, Syrian regime forces "have been emboldened by Donald Trump's victory and the prospect of a US-Russian rapprochement which would focus solely on fighting IS", said Bitar.
- What can be done for civilians? -
The UN's Syria envoy Staffan de Mistura has warned that the ongoing military operation in east Aleppo could lead to a humanitarian "catastrophe".
But the world body has made no headway in securing a truce in the fighting, or even delivering aid to east Aleppo where residents face food and fuel shortages.
The latest assault has hit hospitals and rescue worker facilities, worsening the misery in the east and contributing to the sense that the east will fall sooner rather than later.
"There is nothing to eat, no more hospitals and the bombardment is non-stop," one European diplomat said on condition of anonymity.
"They are under very strong pressure and we could see a repeat of the scenario in Daraya, where after five years they were finally forced to accept evacuation."