|A boy walks amid damaged buildings in the rebel held area of al-Kalaseh neighbourhood of Aleppo, Syria, September 29, 2016.REUTERS/Abdalrhman Ismail|
Syrian government forces made a significant advance, capturing the Handarat refugee camp a few kilometers (miles) north of the city. They had briefly seized it on September 24, before losing it again in a rebel counter attack.
Rebel fighters have launched an advance of their own near the central city of Hama, where they said they made gains on September 29.
The United States and European Union accuse Russia of torpedoing diplomacy to pursue military victory in Aleppo, and say Moscow and Damascus are targeting civilians, hospitals and aid workers to break the will of 250,000 people living under siege in the city.
The United States called the assault on Aleppo by Syria and Russia "a gift" to Islamic State on September 29, saying it was sowing doom and would generate more recruits for the militant group.
Syria's U.N. Ambassador Bashar Ja'afari rejected accusations that his government was killing civilians.
But U.S. officials are searching for a tougher response to Russia's decision to ignore the peace process and seek military victory on behalf of President Bashar al-Assad.
"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 told a public policy conference in Washington.
"It is one of those moments where we are going to have to pursue other alternatives," he added.
Kerry spoke to Russian Foreign Minister Sergei Lavrov on September 29, the U.S. State Department said but it did not announce a suspension of the diplomacy, suggesting Washington may give Moscow a little more time.
Recapturing Aleppo would be the biggest victory of the war for government forces, and a potential turning point in a conflict that until now most outside countries had said would never be won by force.
The multi-sided civil war has killed hundreds of thousands of people, made half the Syrian population homeless, and allowed much of the east of the country to fall into the hands of Islamic State jihadists who are enemies of all other sides.