The United States and Russia grappled over a possible deal on ending the bloodshed in Syria on Friday, as Moscow-backed forces tightened the noose on the beleaguered city of Aleppo. In Geneva, Secretary of State John Kerry was once more locked in talks with Russian counterpart Sergei lavrov but US officials warned talks could not go on forever without a breakthrough.
The two powers back opposite sides in the five-year conflict, with Moscow supporting the regime of President Bashar al-Assad and the US behind a coalition of rebel groups it regards as moderate.
Officials travelling with Kerry said he would not have flown out once again to new face-to-face talks with lavrov unless he thought there was a chance of progress. But they warned there was no guarantee of a final agreement within the narrow window before both men return home, coming just four days after the pair met in China and failed to narrow their differences.