David Cameron (R) greets Russian President Vladimir Putin at 10 Downing Street, London World leaders head to the G8 summit in Northern Ireland looking to put pressure on Russia to back away from its support of Syrian President Bashar al-Assad amid growing Western efforts to arm the rebels. British Prime Minister David Cameron, the host of the meeting of top industrialised powers, insisted he could overcome his differences with Russian President Vladimir Putin after they held pre-summit talks in London.
Hours before the summit was due to begin, Cameron said his priority for the meeting was to ensure a peace conference on the Syria conflict takes place later this year.
But amid rising tensions over Syria, talks between Obama and Russian President Vladimir Putin were set to be prickly, with both leaders now offering military support to opposing sides in the war.
 \"What we can try and do here at the G8 is have further pressure for the peace conference and the transition that is needed to bring this conflict to an end,\" Cameron said in a round of television interviews before the summit began.
\"We (Britain) haven\'t made a decision to give any arms to the Syrian opposition but what we do need to do is bring about this peace conference and this transition, so that people in Syria can have a government that represents them, rather than a government that\'s trying to butcher them,\" he said.
In London, Putin insisted that Moscow had abided by international law when supplying weapons to Assad\'s regime and demanded that Western countries contemplating arming rebels do the same.
\"We are not breaching any rules and norms and we call on all our partners to act in the same fashion,\" Putin said.
The Russian leader referred to a video released last month purportedly showing a rebel Syrian fighter eating the heart of a dead soldier.
He asked if the West really wanted to support rebels \"who not only kill their enemies but open up their bodies and eat their internal organs in front of the public and the cameras\".
But Cameron said: \"What I take from our conversation today is that we can overcome these differences if we recognise that we share some fundamental aims: to end the conflict, to stop Syria breaking apart, to let the Syrian people decide who governs them and to take the fight to the extremists and defeat them.\"
Obama will confront the Russian premier at the G8 after his administration signalled it would begin arming vetted rebels battling Syria\'s government, Russia\'s top Arab ally. He will emphasise to Putin that Washington wants to keep alive a mooted Geneva peace summit co-organised with Moscow, which appears to be slipping down the list of priorities.
That decision last week complicated the already delicate politics of the Obama-Putin meeting and prompted Russia to acidly decry US claims that Syria crossed a \'red line\' by using chemical weapons as unconvincing.
Washington, trying to preserve the troubled notion of a Geneva peace summit co-organised with Moscow, wants a change of strategy from Putin, who has backed President Bashar al-Assad even as Obama has repeatedly demanded he leave power.
But no one expects the Russian leader to yield, especially in the wake of battlefield gains against the rebels by Assad\'s forces bolstered by Hezbollah militia fighters and Iran.
Putin may also be taking some Machiavellian comfort from the public agonising consuming Western governments over what to do about Syria, which has been particularly acute inside the Obama administration.
\"We still continue to discuss with the Russians whether there is a way to bring together elements of the regime and the opposition to achieve a political settlement,\" said Ben Rhodes, a deputy US national security advisor.
\"There are no illusions that that\'s going to be easy.\"
US officials will try to convince Putin that a descent into deeper chaos and instability in Syria is not in Moscow\'s national interests.
Top US officials, keen to avoid in Syria the messy splintering of state institutions that led to chaos in Iraq, are stressing the idea that if Assad leaves, elements of the regime, presumably sympathetic to Russia, might stay.
But the argument\'s potency has weakened given indications that Assad\'s position is more stable than it has been for months.
Obama may press Putin on whether Russia plans to complete the delivery of S-300 anti-aircraft missiles to the Damascus regime -- which could complicate any future US or Western air operations over the country.
Beyond the talks on Syria, Obama will likely probe whether Putin is ready to talk about weapons cuts as he seeks to cement his nuclear arms reduction legacy after agreeing on a new START treaty with Moscow in his first term.