 -- Bodies lie lifeless in the streets of Aleppo’s old city. Rescue workers are unable to pull out the dead fast enough under the unrelenting shelling and bombing by pro-Assad forces on the march.

Two weeks into their renewed offensive on eastern Aleppo, Syria, forces backing President Bashar al-Assad have captured close to 75 percent of the territory controlled by opposition armed factions, including the old city. The fall of eastern Aleppo would grant Assad a strategic victory, returning all urban centers in the country to his control.

Suffering successive defeats, the rebels today proposed a five-day ceasefire in what many see as their Hail Mary, while a defiant Assad said the United States was “begging for a truce” seeing the dire straits the opposition factions were now in.

"Forgive me, I am not capable of saying anything. We will lose Aleppo soon," Ibrahim Hilal, leader of the White Helmets in the city, a volunteer group of rescue workers, told ABC News.

Images of death and devastation abound from eastern Aleppo. While thousands have fled the besieged part of the city over the past two weeks, many remain and continue to endure deafening explosions as well as shortages of the most basic human needs such as food, water, health care and fuel for heating. One photo shows an older man pushing his sick wife in a worn-out wheelchair in a destroyed neighborhood.

“He was looking for a hospital because his wife was very malnourished and there was no food or medicine for her to take,” Yehya Alrejjo, the photographer who took the picture, told ABC News. The only hospital open would take the man five to six hours to reach on foot, the photographer said. So, the man waited, hoping that a car would drive by and pick them up, Alrejjo said.

“He waited and waited for a car. He waited and waited until God took his wife,” Alrejjo said, adding that the man told him that he has seven children and doesn’t know where they are.

Today, armed Syrian opposition factions proposed an immediate truce to evacuate some 500 wounded under U.N. supervision. They said that civilians who wish to leave eastern Aleppo should be evacuated to an area in the northern countryside.

“We are just focusing on securing safe passage for these people now,” said Colonel Abu Bakr of the Jaysh al Mujahideen Islamist rebel group. “We are not discussing any withdrawal by fighters.”

Over the past few weeks, Russia had several meetings in Turkey with representatives of the major armed factions in eastern Aleppo, except for Jabhat Fateh al Sham (JFS) -- formerly the al-Qaeda affiliate Jabhat al Nusra -- to negotiate a settlement. The talks were based on what is known as the U.N. four-point plan that suggested an immediate ceasefire, humanitarian aid deliveries, evacuation of civilians and wounded, as well as the withdrawal of JFS fighters.

“The opposition factions had initially been opposed to the U.N. plan, but they came around to it once the wind turned on the battlefield in recent weeks,” said Bassam Barabandi, a former Syrian diplomat who defected.

The lack of safety guarantees and concrete support from the international community in the face of the Russian onslaught was also to blame for the dramatic deterioration of the situation in eastern Aleppo, according to Barabandi.

The Syrian government rejected the U.N. proposal early on, maintaining that any truce would only be used by the armed factions, which it considers to be terrorists, to regroup.

Negotiations in Turkey petered out when Russia suddenly demanded the withdrawal of all armed factions, not just JFS.

“The Russians are not trustworthy. They are just stalling to finish the job militarily on the ground,” Abu Bakr said in Arabic. “They keep moving the goal post. Their demands never end.”

Six Western nations -- the United States, Canada, France, Germany, Italy and the United Kingdom -- have also called for an immediate ceasefire and denounced the actions in Aleppo of the Syrian government and its Russian backers.

“A humanitarian disaster is taking place before our very eyes,” a joint statement read. “Hospitals and schools have not been spared. Rather, they appear to be the targets of attack in an attempt to wear people down. The images of dying children are heartbreaking. We condemn the actions of the Syrian regime and its foreign backers, especially Russia, for their obstruction of humanitarian aid, and strongly condemn the Syrian regime's attacks that have devastated civilians and medical facilities and use of barrel bombs and chemical weapons.”

Secretary of State John Kerry met tonight in Hamburg, Germany, with Russian Foreign Minister Sergey Lavrov. They discussed ongoing multilateral efforts to achieve a cessation of hostilities in Aleppo, as well as the delivery of humanitarian aid to the tens of thousands of Syrian civilians in desperate need there, according to Assistant Secretary and State Department spokesman John Kirby.

Russian officials have been meeting with representatives of the Syrian rebel factions in Ankara to discuss a solution, two sources close to the negotiations told ABC News. The parties are discussing a deal based on a U.N. proposal that would grant rebel fighters a safe passage out of east Aleppo and leave in place an opposition local council to run the eastern side of the city, effectively keeping it under opposition control.

There have been at least 10 meetings between Russia and rebels so far, the sources said. At this stage, the different armed factions are still weighing whether to take the deal. It remains unclear how Russia would convince its partners, Iran, Hezbollah and the Syrian government, to agree to the deal.

When the Syrian government started its latest offensive on east Aleppo it was the largest remaining opposition stronghold -- retaking it in its entirety is a strategic goal for President Assad.

Among the rebels that Russia has been meeting with are the Free Syrian Army and the Islamist groups Ahrar al-Sham, Noureddine Zenki and Jaysh al Mujahideen. A commander of the latter group told ABC News that the rebels have rejected the Russian proposal to withdraw completely from eastern Aleppo. A diplomat told ABC News that the Russian strategy is to empty east Aleppo of civilians to be free to bomb the rebel forces.

This last-minute proposal might open the opposition factions up to slaughter, according to a Western diplomat who is involved in the Syrian negotiations who said he was surprised by the move.

“The Russian tactic has, since August, been to empty eastern Aleppo from its civilians and hence have carte blanche to carpet bomb the opposition armed factions whom they consider to all be terrorists," the diplomat, who didn’t want to be named because he wasn’t authorized to speak to the press, told ABC News.

Russia’s foreign minister has already said that rebels who stay in the area will be considered terrorists.

"We will treat them as such, as terrorists, as extremists, and will support a Syrian army operation against those criminal squads," Lavrov said during a news conference on Monday.

Some 100,000 civilians are estimated to still be trapped in the rebel-held part of east Aleppo. According to the U.N.’s latest estimates, around 31,500 have been displaced in Aleppo in recent days, about half of them children -- The Syrian Observatory for Human Rights estimates that as many as 80,000 have fled their homes.

“This is what’s happening in my city, in Aleppo,” said resident Yasser Hmeish, via voice recording. “I’m in a hospital. ... I left my family and my wife in my neighborhood this morning. Now I can’t go there because this neighborhood was taken by the regime. I don’t know anything about them -- if they are alive or killed. There is no internet service there.”