Corridors are to open to allow unarmed rebels and civilians to leave besieged areas of the Syrian city of Aleppo, Russia - Syria's key ally - has said.
Three routes would be opened and a fourth for armed rebels, Russian Defence Minister Sergei Shoigu said.
Syria's president has also offered an amnesty for rebels laying down arms and surrendering within three months.
Government forces have encircled Aleppo, cutting off rebel-held areas and severing all supply routes.
The offensive has been aided by Russian air power.
Rebel forces fighting the government of President Bashar al-Assad have held eastern parts of the city for the past four years.
The UN has warned of a critical situation for about 300,000 people still there.
UN humanitarian chief Stephen O'Brien said on Monday that "food supplies are expected to run out in mid-August and many medical facilities continue to be attacked".
Mr Shoigu described the corridors as a "large-scale humanitarian operation".
He said the move was "first and foremost to ensure the safety of Aleppo residents".
The three corridors for civilians and unarmed fighters would have medical posts and food handouts, Mr Shoigu said, adding that he would welcome the co-operation of international aid organisations.
The fourth, in the direction of Castello Road, would be for armed militants, although Mr Shoigu complained that the US had not supplied information about how the rebel Free Syrian Army units it supports had separated from jihadist al-Nusra fighters.
Reports on Thursday said that government forces had taken control of more areas of the city, in the Bani Zeid neighbourhood.
Mr Assad's amnesty offer came in a decree issued on Thursday, the state-run Sana news agency reported.
"Everyone carrying arms... and sought by justice... is excluded from full punishment if they hand themselves in and lay down their weapons," it quoted the decree as saying.
There have been several presidential amnesty offers in recent years.
Offer met with distrust - BBC's Caroline Hawley
Throughout the five years of Syria's war, aid agencies have pleaded for humanitarian access - usually in vain. Only under intense international pressure has the regime allowed a limited number of aid convoys to reach areas under siege. But now, with the rebels surrounded in Aleppo, the Syrian government may feel it can afford to appear magnanimous.
The announcement has taken many by surprise but may be modelled on a ceasefire agreement last year in Homs.
That deal allowed starving rebels to leave, ceding control of the city to the government. Winning back Aleppo - Syria's biggest city - would be a huge prize for the government. But so far there are no signs of fighters leaving the city. Rebels and civilians alike have reacted to the initiative with intense distrust.
Last week US Secretary of State John Kerry held marathon talks in Moscow with Russian President Vladimir Putin and his Foreign Minister Sergei Lavrov.
They agreed "concrete steps" on tackling jihadists in Syria and on trying to reach an effective ceasefire, although proposals have not been made public.
More than 280,000 people have been killed and millions displaced since the Syrian conflict began in March 2011.