Russia and the United States are close to starting joint military action against militants in Syria's Aleppo, Russian news agencies on Monday quoted Defence Minister Sergei Shoigu as saying.
Fighting for control of the divided city of some 2 million people has intensified in recent weeks and there have been some gains for rebel groups battling Syrian government forces.
Russia backs Syrian President Bashar al Assad in the five-year-old Syria conflict, while the United States wants to see Assad step down. But both are participating in talks to try to find a political solution to end the civil war.
Senior Russian and US military officials have held Geneva negotiations on Aleppo and on restoring an overall ceasefire, UN Special Envoy for Syria Staffan de Mistura said last Thursday.
"We are now in a very active phase of negotiations with our American colleagues," the RIA news agency cited Shoigu as saying. "We are moving step by step closer to a plan — and I'm only talking about Aleppo here — that would really allow us to start fighting together to bring peace so that people can return to their homes in this troubled land."
Asked about Shoigu's remarks, US State Department spokeswoman Elizabeth Trudeau told reporters in Washington: "We have seen the reports and have nothing to announce … We remain in close contact [with Russian officials]."
Trudeau said the United States continued to push for a broader cessation of Syria hostilities accord with Russia.
The battle for Aleppo is "one of the most devastating urban conflicts in modern times," Peter Maurer, president of the International Committee of the Red Cross (ICRC), said on Monday.
"No one and nowhere is safe. Shellfire is constant, with houses, schools and hospitals all in the line of fire. People live in a state of fear. Children have been traumatized. The scale of the suffering is immense," Maurer said in a statement.
The ICRC reiterated its call on all warring parties to allow humanitarian agencies to deliver supplies to civilians in desperate need of food and clean water across Aleppo.
Russia has delivered aid to Aleppo and is helping to rebuild damaged water pumping stations, Shoigu said. About 700,000 people are still living in Aleppo and residents in the eastern part of the city were "hostages of armed groups", he added.
Earlier on Monday, Russian Foreign Minister Sergei Lavrov said that Syrian militants had used a temporary ceasefire around Aleppo to regroup.
Deputy Foreign Minister Mikhail Bogdanov said Iran, Turkey and Saudi Arabia should play a more active role in helping to resolve the Syria crisis.
"[They should] sit down at the table and negotiate," Bogdanov told RIA news agency, saying he would meet representatives of the Syrian opposition in the Qatari capital, Doha, on Aug. 16.
But the official spokesman for the Syrian opposition High Negotiations Committee (HNC), Riad Nassan Agha, said on Monday the HNC was unaware of this meeting. He said it did not know which "opposition" Bogdanov was referring to.