The US is threatening to cut off all contact with Moscow over Syria, unless Russian and Syrian government attacks on Aleppo end.
A spokesperson for the US Secretary of State said that Washington holds Moscow responsible for the situation in Syria, including the use of incendiary and bunker-buster bombs in an urban environment.
In a telephone call to Russian Foreign Minister, Sergey Lavrov, John Kerry expressed grave concern over attacks on hospitals, water supplies and other civilian infrastructure in Aleppo.
Mr Kerry told Mr Lavrov the US was preparing to "suspend US-Russia bilateral engagement on Syria", including on a proposed counter-terrorism partnership, "unless Russia takes immediate steps to end the assault on Aleppo" and restore a cease-fire.
Mr Lavrov replied that the US must separate opposition groups and terrorists in Syria.
The situation in Aleppo is worse than a slaughterhouse, UN Secretary General Ban Ki-moon has said.
Mr Ban's comments were made at a UN Security Council meeting just hours after Russian or Syrian warplanes bombed two hospitals in the besieged city.
A slaughterhouse is "more humane" than the current situation in Aleppo, he added.
Mr Ban continued: "Hospitals, clinics, ambulances and medical staff in Aleppo are under attack around the clock.
"According to Physicians for Human rights, 95% of medical personnel who were in Aleppo before the war have fled, been detained or killed.
"This is a war against Syrian health workers."
Former England boss Steve McClaren says anyone could have been caught out like Sam Allardyce.
The ex-Bolton manager lost the England job on Tuesday following comments he made to undercover reporters.
McClaren, who was speaking at the SoccerEx conference in Manchester, expressed his disappointment for Allardyce on a personal level, after he only lasted 67 days as England manager.
Extremist preacher Anjem Choudary has applied for permission to appeal against his conviction for drumming up support for so-called Islamic State (IS), the Judicial Office has said.
He was jailed for five and half years at the Old Bailey earlier this month.
The father-of-five spread extremist views by encouraging people to back IS in a series of speeches posted on Youtube.
He finally fell foul of the law after spending 20 years as a thorn in the side of UK authorities, with a string of former supporters going on to be convicted of terrorism.
Union leaders Len McCluskey and Dave Ward have praised Jeremy Corbyn's closing speech at the Labour party conference.
Len McCluskey, general secretary of Unite, said Mr Corbyn was determined to rebuild trust in politics.
Dave Ward, leader of the Communication Workers Union, said: "Jeremy Corbyn deserves the time and space to set out his vision for our country. Today he looked and sounded like a leader.
"We urge the whole Labour Party to unite behind our leader, who holds the largest mandate in history. Let's create a society for the millions not the millionaires."
Unison general secretary Dave Prentis said the speech was 'ambitious'.
He said: "We must ignore the doom mongers, the next election is not lost, but the year ahead has to be about how Labour wins back the support of voters across the country."
Josh Hardie, CBI deputy director-general, said: "The CBI shares much of Labour's vision for a fairer society underpinned by good business.
"Labour is certainly laying out a new way forward and we urge them to iron out inconsistent messages - especially the relationship between state and industry - and clarify policies that are sometimes hard to see delivered and paid for."
Labour will offer a socialism 'fit for the 21st Century' in order to win the next election, leader Jeremy Corbyn has pledged.
Mr Corbyn insisted that the party would fight for its long-terms goals of "equality of wealth and income" but "also for power".
He was speaking as the party's conference in Liverpool came to a close.