Vladimir Putin may allow Assad to go if power vacuum in Syria is avoided

The Russian president, Vladimir Putin, is willing to see the removal of the Syrian leader Bashar al-Assad, but only if it leads to a balanced government and not a dangerous power vacuum of the kind that followed Saddam Hussein's removal in Iraq, British officials believe after two days of intensive talks at the G8 summit.

Putin blocked any reference in the subsequent communique to the removal of Assad, but British officials believe the talks have opened the way for a peace settlement if more can be done to organise the Syrian opposition forces politically and militarily.

Talks over the terms of the communique lasted until 3am. The Russians accepted the need for UN weapons inspectors to visit Syria to check on western claims that Assad has used chemical weapons.

But Putin flatly refused to have any reference in the communiqué to the nature of delegations that should be sent to the planned Geneva peace conference, insisting that this was a matter for both sides.

British officials insisted that in private Putin had declared no personal allegiance to Assad, but needed assurances that Syria would not turn into an ungoverned space on Russia's borders if he were removed. David Cameron in his press conference at the end of the summit made repeated calls for Assad's allies to realise that a strong army and security state would be preserved during a transition, words designed to reassure them that they would have a future after Assad.

British officials admitted that the Syrian opposition was still a work in progress. They had been unable to agree a negotiating mandate for a new peace conference.

The G8 communique made no reference to Assad, but called for peace talks to be resumed as soon as possible. Cameron said the main breakthrough was an agreement that a transitional government with executive powers was needed, together with a deal to call for an investigation into chemical weapons use. "We remain committed to achieving a political solution to the crisis based on a vision for a united, inclusive and democratic Syria," the final communique read. "We strongly endorse the decision to hold as soon as possible the Geneva conference on Syria."

Putin struck a defiant tone in public, telling the west that sending weapons to rebels could backfire one day, while he defended his own military contacts with the Syrian government.

"There are different types of supplies. We supply weapons based on legal contracts to a legal government … And if we sign these contracts [in the future], we will supply [more arms]."

In the final document, G8 leaders also called on the Syrian authorities and the opposition to commit to destroying all organisations affiliated with al-Qaida, a reflection of growing concern in the west that Islamist militants are playing a more dominant role in the rebel ranks.

Cameron, who chaired the summit, said separately after the talks that the west believed strongly that there was no place for Assad in a future Syria. "It is unthinkable that President Assad can play any part in the future of his country. He has blood on his hands. You can't imagine a Syria where this man continues to rule having done such awful things to his people."

He appealed to Assad's acolytes to abandon the president, insisting the need for the retention of a strong security force showed they would have a future role in Syria. He said the aim was "to learn the lessons of Iraq by ensuring the key institutions of the state are maintained through the transition and there is no vacuum. 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 of this point".

Russia's deputy foreign minister, Sergei Ryabkov, speaking on the sidelines, said earlier that any debate about Assad's role in the resolution of the conflict was unthinkable, adding he would not tolerate an outcome that led to Assad's capitulation. "This would be not just unacceptable for the Russian side, but we are convinced that it would be utterly wrong, harmful and would completely upset the political balance," Ryabkov said.

In a further development, the French president, François Hollande, opened the door to Iran attending a Syria peace conference, but reiterated that there was no future for Assad.

Paris had previously ruled out Iran taking part in the proposed conference, saying Tehran had no desire for peace, but a new Iranian president, Hassan Rouhani, was elected on Friday.

"There will no future for Syria with Assad. The Russians are not yet ready to say or write it, but when we speak of transition ... it's difficult to see how he (Assad) could be responsible for it," Hollande said.British officials said they did not rule out Iran attending talks, but needed to know more about the new president and what he would do about the Iranian-backed Hezbollah forces in Syria.