GENEVA (Reuters) - The U.N. Special Envoy for Syria offered on Thursday to go to eastern Aleppo and escort up to 1,000 Islamist fighters out of the city to try to bring an end to bombardment by Russian and Syrian forces.

U.N. mediator for Syria Staffan de Mistura reacts after a news conference at the United Nations in Geneva, Switzerland October 6, 2016. REUTERS/Denis Balibouse

Staffan de Mistura said history would judge Syria and Russia if they used the presence of about 900 former Nusra Front fighters as an “easy alibi” for destroying the rebel-held area where 275,000 residents, 100,000 of them children, are besieged.

“The bottom line is in a maximum of two months, two and a half months, the city of eastern Aleppo at this rate may be totally destroyed,” de Mistura told a news conference in Geneva.

Since the aerial bombing intensified on September 23rd, 376 people have been killed, one third of them children.

De Mistura said there were a maximum of 8,000 rebels in eastern Aleppo. Many ex-Nusra fighters left before the area was encircled and no more than 900 remain, he said, before addressing them directly.

“If you did decide to leave, in dignity with your weapons, to Idlib or anywhere you wanted to go, I personally am ready, physically ready, to accompany you,” he said. “I can’t guarantee more than my own personality and body.”

This year the United Nations has overseen an attempt to negotiate peace in Syria using U.S. and Russian pressure to bring the two sides together. It began fitfully, stalled, and collapsed this week with Washington’s suspension of cooperation with Moscow, prompted by Russia’s bombing in eastern Aleppo.

Russia says it is targeting banned terrorists in eastern Aleppo and blames the United States for not separating former Nusra fighters, now renamed Jabhat Fateh al Sham, in an apparent attempt to sever its links with al Qaeda, from other rebels.

De Mistura’s offer to escort fighters out of eastern Aleppo was quickly backed by Russian presidential envoy Mikhail Bogdanov.

“It’s high time,” TASS news agency quoted him as saying in response to de Mistura’s proposal. It was not immediately clear if Russia was also willing to stop its bombing, which has enabled Syrian government forces to make advances.

President Bashar al-Assad, whose government has described all armed groups seeking his overthrow as terrorists, said in an interview with Danish television that his forces would recapture all of Syria. But he said he would prefer to do so using local deals and amnesties that allow rebels to leave for other areas.

De Mistura said the choice was between destroying the whole city of eastern Aleppo, home to 275,000 people, for the sake of eliminating about 1,000 Nusra fighters, or letting the Nusra fighters leave and halting the bombing.

The latter option would leave the local administration in place and enable humanitarian and medical aid to reach the population, including at least 200 wounded civilians who need medical evacuation to save their lives.