Matt Chorley,
POLITICAL EDITOR FOR MAILONLINE
Desperate world leaders today lined up to try to woo Russian President Vladimir Putin to back global efforts to defeat ISIS.
For more than a year relations with Moscow have been in the deep freeze over Russian incursions in Ukraine.
But now Mr Putin is seen as holding the key to resolving the bloody civil war in Syria which has given rise to ISIS fanatics.
It has led to the spectacle of US President Barack Obama, British PM David Cameron and Saudi Arabia's King Salman bin Abdulaziz Al Saud posing for photos with the Russian President.
Desperate world leaders today lined up to try to woo Russian President Vladimir Putin to back global efforts to defeat ISIS
US President Barack Obama appears to share a joke with Mr Putin in sign of relations with Moscow thawing
The Kremlin has been accused of using a campaign of airstrikes to target opponents of Syrian president Bashar Assad and not ISIS strongholds.
But world leaders now accept there is little hope of degrading and destroying ISIS without the co-operation of Russia.
Mr Cameron today offered 'compromises' to Russia on the future of Syrian dictator Assad in return for help targetting ISIS.
Britain's olive branch to to Russia comes after US President Barack Obama sat down with Mr Putin for crucial talks on the sidelines of the G20 summit last night.
Both countries have pledged to eliminate ISIS and end the Syrian war that has fueled its rise.
Mr Cameron used face-to-face talks with Mr Putin in the Turkish beach resort of Antalya - just 300 miles from the Syrian border - to urge him to turn Russia's firepower on ISIS.
But he also made clear that Britain is prepared to make 'compromises' with Russia, potentially including on the future of Assad.
Mr Cameron insisted that the issue of the future of Assad must not become 'the alter on which the country of Syria is slaughtered'.
Mr Obama and British Prime Minister David Cameron walk together at the G20 summit in Antalya, Turkey where they have urged Mr Putin to do more to tackle ISIS
Britain is prepared to make 'compromises' with Russia to secure the defeat of ISIS, David Cameron said today as he met Vladimir Putin at the G20 summit in Turkey
The British Prime Minister held urgent one-to-one talks with the Russian President over how to resolve the bloody civil war in Syria which has given rise to ISIS fanatics
Mr Cameron and Mr Putin posed awkwardly for photographs at the start of this morning's meeting at the G20 summit in Turkey, the first time the two men have met face-to-face for a year.
Britain, together with the United States, France, Germany and Italy, is trying to reset relations with Moscow which were badly damaged by Russian incursions into Ukraine.
It is hoped the the death of 224 on board the Russian Metrojet Airbus in Egypt last month - thought to have been brought down by an ISIS bomb - will help to secure Russia's help in targetting ISIS.
Mr Cameron offered Mr Putin his condolences for the Metrojet attack and told him: 'We are meeting together after the appalling terrorist attacks in France, and it is clear to me that we must work together to defeat this scourge of terrorism that is a threat to Britain, a threat to Russia and a threat to us all.'
Following the hour-long meeting, the Prime Minister insisted that the refusal of the UK, US and Saudi Arabia to give ground on the need for Assad's removal was not a matter of 'pride or stubbornness' but a recognition of the political reality that he would not be accepted as leader by many Syrians who had suffered under his rule.
'The gap has been enormous between those of us who believe Assad should go immediately and those like President Putin who have been supporting him and continue to support him. I think everyone recognises the need for compromise,' he said.
'That's the gap we have. I think it has been reduced and the talks in Vienna between foreign ministers, I hope, can close the gap still further.
'There is still a very big gap, but I think there's some hope that this process could move faster in the future than it has in the past.'
Mr Putin told Mr Cameron that UK-Russian relations were 'not in the best shape', but thanked him for sharing UK intelligence in a phone call following the Sharm crash and added: 'The recent tragic events in France show that we should join efforts in preventing terror.'
Mr Putin was pictured smiling and posing for photos with Chinese President Xi Jinping during the G20 summit in Turkey
The Russian President was also feted by Saudi King Salman bin Abdulaziz Al Saud during a meeting on the sidelines of the G20 summit in Antalya (left) and German Chancellor Angela Merkel
Mr Putin later signed a copy of the photo to mark the gathering at the Turkish beach resort of Antalya - just 300 miles from the Syrian border
World leaders each signed their names around the frame of a family photograph taken to mark the end of the two-day conference
Mr Putin claims the campaign of airstrikes he launched in September is directed at 'terrorists', but the West accuses him of instead targeting the forces of the moderate opposition ranged against Assad.
Mr Cameron told BBC Radio 4's Today programme: 'The disagreement has been that we think that Assad should go at once and obviously Russia has taken a different view.
'We have to find a settlement where Assad leaves and there is a government that can bring Syria together and we mustn't let the gap between us be the alter on which the country of Syria is slaughtered.
'That is the challenge. Now that is going to take compromises.'
He insisted that it was not the West which had decided Assad must go, but his own barbaric behaviour which meant he can play no part in Syria's future.
'This man has barrel bombed his own population, slaughtered so many people. It's unthinkable for the Syrian people - not just for us - that he could play a long term role in running the country.
Downing Street later said that Mr Cameron and Mr Putin had a 'constructive, measured discussion' lasting about an hour, of which terror and the situation in Syria took up around 40 minutes.
Officials said there were indications that the Russian president was ready to talk about the details of the transition process in Syria and there was 'some reason for optimism', though there was still 'a long way to go'.
Mr Cameron's offer to Russia comes after US President Barack Obama sat down with Mr Putin for crucial talks on the sidelines of the G20 summit last night.
Both countries have pledged to eliminate ISIS and end the Syrian war that has fueled its rise.
Their huddle over a coffee table in Antalya, Turkey, was the first time that the two leaders had seen since Russia started air strikes over Syria in September.
President Barack Obama sat down with Russian President Vladimir Putin for crucial talks on the sidelines of the G20 summit. Joining them were Obama's national security adviser Susan Rice and a Russian aide
They chatted in a foursome with Obama's national security adviser Susan Rice and a Russian aide.
Their meeting was visible on a television feed provided by the summit's host country but their conversation could not be heard.
The White House says the 35-minute encounter centered on talks to end Syria's civil war and that the two leaders agreed that the country needs a political transition led by Syrians. The transition would be preceded by negotiations mediated by the United Nations and a cease-fire.
Mr Obama and Mr Putin have long been at odds about whether Syrian President Bashar Assad can maintain a role following that transition
The two leaders also discussed the conflict in Ukraine and Mr Obama expressed condolences for the victims in the Russian plane crash in the Sinai Peninsula last month.
They also discussed a new proposal to end the Syrian conflict and Mr Obama's hope that Russia's airstrikes in Syria will focus on ISIS, not opposition groups fighting Assad.
Reporters were not allowed in for the meeting, which took place during a working lunch for leaders attending the summit.
Obama and Putin both leaned in close to each other as they talked, with the former gesturing expressively with his hands.
During the talks with world leaders, Obama said 'the skies have been darkened' by the attacks in Paris.
He vowed to stand in solidarity with France and aid the effort to hunt down the perpetrators and bring them to justice.
However, he offered no details about what the US or its coalition partners might do to step up its assault against ISIS.
Mr Obama and Mr Putin have long been at odds about whether Assad can maintain a role following that transition.
Mr Obama also renewed his call for Russia to withdraw forces, weapons and support for pro-Russian rebels in Ukraine, the White House said.
Putin's foreign affairs adviser, Yuri Ushakov, told reporters that Putin and Obama had a 'quite detailed conversation,' with Syria taking most of the time. He said they talked about the terror attacks in Paris and other terrorism-related issues.
'Strategic goals related to fighting the ISIL are very close, but tactical differences remain,' Ushakov said.
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