Russia warned on Tuesday that the next round of Syria peace talks should not be contingent on a halt to fighting in Aleppo after U.N. Syria envoy Staffan de Mistura told the U.N. Security Council he aims to reconvene negotiations in late August.

Speaking after a closed door meeting of the 15-member council, Russian U.N. Ambassador Vitaly Churkin told reporters: “The lower the level of violence the better it is for the talks… but there must be no preconditions for the talks.”

Insurgents effectively broke a month-long government siege of eastern, opposition-held Aleppo on Saturday, severing the primary government supply corridor and raising the prospect that government-held western Aleppo might become besieged.

Churkin called on countries with influence over the Syrian opposition to make sure they are prepared for future talks.

“They were coming to the talks without saying anything, they were just saying (Syrian President Bashar) ‘Assad must go’ and this is not a negotiating position,” he said.

Russia and the United States are both conducting air strikes in Syria against Islamic State fighters, but support opposing sides in a wider civil war, with Moscow backing Assad’s government and Washington saying he must leave office.

Peace talks broke up last April after the opposition delegation quit, accusing the government of ignoring a cessation of hostilities brokered in February.

U.S. Ambassador to the United Nations Samantha Power said the Syria peace talks urgently need to get back on track but “the environment for talks also has to be right.”

“On humanitarian access… we’re in reverse gear. On the cessation of hostilities, we’re back to where we were before the cessation of hostilities, with the additional negative of Aleppo being besieged,” Power told reporters.

The United Nations has been calling for a weekly 48-hour pause in the fighting to access Aleppo. U.N. aid chief Stephen O’Brien, who also briefed the council, said talks were ongoing.

Churkin said the United States and Russia were “very practically” discussing in Geneva how aid could be delivered to Aleppo and that Moscow supported a 48-hour pause in fighting, but that such a truce “does not apply to terrorists.”

The United Nations said on Tuesday that two million people lack access to clean water in Aleppo, creating a risk of disease. It said technicians need access to repair electricity networks that drive water pumping stations.