An army of 10,000 troops is amassing outside of the besieged city of Aleppo as the government prepares for an unprecedented assault on rebel-held areas of the city after a week of airstrikes and artillery fire has left the city burning and hundreds dead.

According to senior government sources speaking to CNN, the US is now considering how to react to the latest move by Syrian President Bashar al-Assad against opposition forces in eastern Aleppo.

The troops, which have been gathering for the last week and are believed to include as many as 3,000 soldiers from Iran, are reportedly preparing for a final ground assault as al-Assad looks to crush rebel positions in eastern Aleppo and retake the strategically important city.

More than 270,000 civilians are trapped in the eastern part of the city according to the World Health Organization, cut off from aid and with "dwindling supplies of food, water and fuel." In recent days the Syrian government has targeted hospitals and bakeries as it seeks to cut off all vital services.

Attacking health care is both illegal & barbaric. Blocking populations from access to medical care, food & water is intolerable — WHO (@WHO)September 30, 2016

On Friday Reuters reported fierce battles had already started in northern Aleppo, with government troops succeeding in capturing the Handarat refugee camp, a few miles from the city. Multiple reports — including video of the attack — also suggest they recaptured the strategically important Kindi hospital which had been held by the Fatah Halab coalition of rebel groups. However Reuters quote rebel sources denying that the government had captured the Kindi hospital area, saying fighting was still going on.

The World Health Organisation on Friday said that fighting in eastern Aleppo has claimed the lives of 338 people in the past few weeks, including 106 children. The charity save the children said that as a result of the unprecedented bombing campaign carried out by Syrian and Russian warplanes over the last week, 10,000 children would not be starting school as intended on Saturday.

"We're now more likely to see children being pulled from the rubble or treated on the floor of a hospital than sat at a school desk," Nick Finney, Save the Children's north west Syria country director, said. "The use of bunker busting bombs means there is literally nowhere we can keep children safe, and we want to see the use of these weapons investigated as a potential war crime."

Speaking at the Washington Ideas Festival on Thursday, US Secretary of State John Kerry said a complete breakdown in relations with Moscow was a real possibility.

"We are on the verge of suspending the discussion because it is irrational in the context of the kind of bombing taking place to be sitting there trying to take things seriously," Kerry said. "It is one of those moments where we are going to have to pursue other alternatives."

The US is not yet preparing plans for any military intervention according to sources speaking to CNN, but it is considering all options including military action and economic sanctions.