The US ambassador to the United Nations, Samantha Power, has labelled Russia's action in Syria as barbarism, not counter-terrorism.
Russia backs Syrian President Bashar al-Assad against rebels seeking to topple him.
The United Nations special envoy on Syria Staffan de Mistura told the same meeting he was convinced the situation in Syria could still be turned and said he would not quit, as Russia and the United States try to salvage a ceasefire.
Meanwhile French Foreign Minister Jean-Marc Ayrault says Russia and Iran would become accomplices in war crimes if they continued to prolong the war in Syria.
Describing Russia and Iran as supporters of Syrian President Bashar al-Assad, Mr Ayrault called on them "to take their responsibility by stopping this strategy that leads to a dead-end".
"Otherwise, Russia and Iran will become accomplices of the war crimes committed in Aleppo," the minister said in a written statement on Sunday with reference to the bombings that struck the Syrian city and killed scores of people.
This comes as the two allies bombed a strategic camp on the northern edge of Aleppo after losing control of it overnight, both rebels and the Syrian army say.
Rebels said the army used more powerful weapons in an attempt to recover Handarat, a Palestinian refugee camp a few kilometres north of Aleppo which is on elevated ground overlooking one of the main roads into Aleppo that had been in rebel hands for years.
"We retook the camp, but the regime burnt it with phosphorous bombs ... We were able to protect it, but the bombing burnt our vehicles," said Abu al-Hassanien, a commander in a rebel operations room that includes the main brigades fighting to repel the army assault.
The army which is being helped by Iranian-backed militias, Lebanon's Shi'ite Hezbollah militant group and a Palestinian militia, acknowledged rebels had retaken Handarat, whose capture on Saturday briefly marked the first major ground advance by the army in a new offensive to recapture rebel held Aleppo.
"The Syrian army is targeting the armed groups' positions in Handarat camp," a military source was quoted on state media as saying.
The army announced on Thursday the start of a major new military campaign to regain Aleppo, intensifying strikes and use of powerful weapons that rebels said was a "shock and awe" campaign aimed at creating devastation and demoralising them.
Russian planes also continued their pounding of residential parts of Aleppo, with whole buildings flattened, according to rebels and residents.
The assault on Aleppo, where more than 250,000 civilians are trapped, could be the biggest battle yet in a civil war that has killed hundreds of thousands of people and driven 11 million from their homes.