Putin agreement pressures Assad All in the family: Vladimir Putin, David Cameron and Barack Obama during the meeting of world leaders. Russian President Vladimir Putin agreed to sign a statement at the G8 summit calling for the establishment of a "transitional government" in Syria as quickly as possible, putting more pressure on Syrian President Bashar al-Assad. The text of the statement on Syria called for "a transitional governing body with full executive powers, formed by mutual consent," while stopping short of calling for Dr Assad's departure. British Prime Minister David Cameron said it was "unthinkable" that a transition government could include Dr Assad. The call came as troops loyal to the Syrian regime were reported to have pushed forward in a bid to crush rebel bastions near the capital Damascus. The British-based Syrian Observatory for Human Rights said troops on Tuesday battled rebels in Zamalka and Mleiha east of Damascus, maintained a siege on Douma, also in the east, and fired on Daraya and Moadamiyet al-Sham, south-west of the capital. The G8 declaration says the leaders endorse a negotiated end to the civil war and commits $US1.5 billion ($1.58 billion) for humanitarian aid to Syrian refugees. Mr Putin was isolated among fellow G8 leaders for backing Dr Assad in a bloody conflict that is estimated to have killed more than 93,000 people. A British official, who asked not to be identified, called the summit a clarifying moment in differences over Syria. While backing a transitional government marked a move towards the position of the US and other Western nations, differences remain. Mr Putin said there was no proof the Syrian government has used chemical weapons, as stated by the US, Britain and France. After an earlier meeting with French President Francois Hollande, US President Barack Obama said both governments "have strong evidence" that chemical weapons have been used in Syria. But the G8 agreed only to call for an investigation into whether such weapons have been used. Mr Putin also reiterated that arming the rebels might further destabilise the situation. He said Dr Assad's opposition included extremists. Ben Rhodes, a White House deputy national security adviser, said the US was "pleased with the language" in the G8 declaration. The next step would be a meeting of representatives from the US, Russia and the United Nations next week, he said. We want the Russians to work with the regime to make sure they come to the table in a serious fashion. Mr Cameron made a direct offer to Dr Assad's supporters within Syria. "To those who have been loyal to Assad but who know he has to go, and who want stability in their country, they should take note at this point," he said. Let's get on with the process of naming people from the regime, from the opposition that can sit down and talk. Bloomberg, AFP