Kerry hopes to work with Russia on Syria

U.S. Secretary of State John Kerry said Washington and Moscow, who support opposing sides in Syria's five-year-old conflict, had made progress in recent days towards working more closely together.

The proposals would have the two powers share intelligence to coordinate air strikes against the al Qaeda-affiliated Nusra Front and prohibit the Syrian air force from attacking rebel groups labeled as moderate.

Efforts to bridge the divide between the United States and Russia and bring Syrian government and opposition forces back to negotiations come after pro-government forces have effectively put rebel-held districts of Aleppo under siege.

Concern is growing for at least 250,000 people who have been trapped in rebel-controlled eastern Aleppo since early July, and the United Nations aid chief asked on Monday for weekly 48-hour pauses in fighting to allow food and aid to be delivered.

Syrian state television said on Tuesday the army had sent text messages to residents and fighters in eastern Aleppo, saying it will grant safe passage to whoever wants to leave and asking militia to put down their weapons.

The Syrian Observatory for Human Rights monitoring group said 25 people, including three women and eight children, were killed in the last 24 hours in the Mashhad quarter of rebel-held Aleppo, when it was hit by barrel bombs thrown from helicopters.

In Geneva, U.N. Special Envoy for Syria Staffan de Mistura said he aimed to convene a new round of peace talks toward the end of August, quietly scrapping a previous Aug. 1 deadline to reach agreement on a framework for a political transition.

"Our aim, let me say very clearly, is to proceed with a third round of intra-Syrian talks towards the end of August," De Mistura told reporters after meeting U.S. Syria envoy Michael Ratney and Russian Deputy Foreign Minister Gennady Gatilov.

De Mistura said he strongly hoped Kerry and Russian Foreign Minister Sergei Lavrov would make concrete and visible progress because that would improve the situation on the ground and the environment for the peace talks, although such progress was not a precondition for talks.