GENEVA: The UN special envoy on Syria said he hoped a meeting between the US and Russian foreign ministers on Wednesday would give impetus to peace talks where the divisive issue of a political transition is stalling progress. Syria's government delegation has rejected any discussion of the future of President Bashar al-Assad, who opposition leaders say must go as part of any transition. Damascus has repeated its long-held view that 'counter-terrorism' - its reference to rebel foes of Assad - should be the main focus of the process. 'We are looking with great interest, expectation, hope that the talks in Moscow will be productive,' UN envoy Staffan de Mistura said after meeting the opposition High Negotiations Committee (HNC) in Geneva. 'Honestly not everything will be solved in one day - but (it would be) productive ... to resume the talks with a much more in-depth address on the issue of political transition,' he said ahead of the planned meeting in Moscow between US Secretary of State John Kerry and Russian counterpart Sergei Lavrov. De Mistura, who tried to keep an air of optimism before the talks adjourn on Thursday, describes Syria's political transition as 'the mother of all issues.' Emboldened by the Russian and US muscle that pushed the warring parties to the negotiating table, he has refused to drop the subject. After five years of conflict that has killed over 250,000 and caused the world's worst refugee crisis, Washington and Moscow engineered a deal three weeks ago for a cessation of hostilities and crucial humanitarian aid to besieged regions. But the deal, not signed by any of the warring parties, remains fragile and diplomats are concerned that, after more than a week of talks, it is at risk of collapsing unless headway on the matter of political transition is made soon. 'We always needed some help from Mr Kerry and Mr Lavrov because they proved in the past and I hope they will prove in the future that when they do have a common understanding, it helps enormously the process,' de Mistura said. Russia, along with Iran, have been Assad's major allies in the conflict, while the United States and Gulf Arab powers have backed rebel forces to varying degrees. On Monday, the head of Syria's government delegation rejected any talk on the fate of Assad, reiterated that the Geneva talks must concentrate on counter-terrorism. Bashar Ja'afari accused de Mistura, a veteran Swedish-Italian diplomat, of 'filibustering' and 'wasting time' after Damascus received no responses to proposals made a week ago. Arguments over Assad's fate were a major factor in the failure of UN efforts in 2012 and 2014 to end the civil war. BARREL BOMBS, AID DELIVERIES Asaad al-Zoubi, head of the main opposition council's delegation, said on Tuesday it was 'obvious that are no points of convergence' with the Syrian government. 'There is a risk – and I don’t know where the breaking point is – that if these talks go on without leading anywhere without coming close to the essential issue of transition, that surely there is a breaking point where the opposition will feel what is the use?' a Western diplomat told Reuters in Geneva. For the first time during the latest round of talks, the opposition accused the Syrian government of strengthening existing sieges, initiating new ones and stepping up a campaign of barrel-bombing across the country. 'The government continues to flout international resolutions,' Zoubi said. 'Instead of lifting the sieges, the regime is tightening sieges on cities and ... the regime is renewing again its barrel-bombing of Syrian towns.' A diplomatic source close to the talks said there were reports of barrel bomb attacks in the rebel-held eastern Damascus suburb of Ghouta. Rami Abdulrahman, director of the Syrian Observatory for Human Rights which monitors the war through a network of contacts on the ground, said fighting had resurged in the Ghouta area in recent days. Russia's Defence Ministry said on Tuesday it had registered six ceasefire violations over the past 24 hours in other areas of Syria. The fragile cessation of hostilities agreement has, however, reduced violence in western Syria, allowing more aid to be delivered. A group of Syrian villages north of Homs under siege by government forces since 2012 received on Tuesday the first delivery since October last year, according to the Swiss-based International Committee of the Red Cross (ICRC). A convoy of 27 trucks containing medical, food, water treatment and other aid was sent to al-Houla, a rural district containing five villages and over 70,000 people, an ICRC spokesman said. In coming weeks, the ICRC plans to enter other areas in northern rural Homs such as Rastan, Talbiseh, Ghanto, Termalie and Dar Kbiereh, where an estimated 270,000 people live.