Leaders from the world's top 20 industrial powers meet in Turkey from Sunday seeking to overcome differences on a range of issues including the Syria conflict, the refugee crisis and climate change.
With the health of the global economy less of a headache than in previous years, it is the war in Syria that will cast the longest shadow at the two-day Group of 20 summit in the Mediterranean resort of Antalya.
The glitzy five-star venue may seem far from the tragedy of the conflict that has left over a quarter of a million people dead, but the border with Turkey's conflict-torn neighbour is just 600 kilometres (370 miles) away.
Security will be tight even by the draconian standards of previous such meetings, with some 12,000 police on duty and the authorities conducting raids in search of Islamic State (IS) militants who have slipped over the border from Syria.
The meeting is the biggest gathering of world leaders ever hosted by Turkey and gives President Recep Tayyip Erdogan the perfect opportunity to present himself as a key global player two weeks after his party regained its overall majority in a parliamentary election.
"I pray and hope that G20 will provide a platform whereby all of these issues can be discussed openly and then we can understand each other," Erdogan told CNN ahead of the summit.
With Moscow at the centre of controversy over its air bombing campaign in Syria, no formal bilateral meeting is scheduled between President Barack Obama and Vladimir Putin of Russia, US and Russian officials said.
But it appears likely the pair will have some informal contact. "We fully expect they'll have ample opportunity for discussion directly," said US national security advisor Susan Rice.
Erdogan and Obama meanwhile are expected to have their first formal face-to-face bilateral encounter since October 2014.
- 'Breakthrough unlikely' -
But finding agreement on Syria will be tough, with Russia vehemently opposed to host Turkey's strategic aim of toppling President Bashar al-Assad and Ankara so far only receiving a lukewarm response to its plan of a safe zone inside Syria.
"A breakthrough is very unlikely on Syria or the refugee question," said Ozgur Unluhisarcikli, Ankara office director for the German Marshall Fund of the United States.
At the same time, he said the G20 would "want to end on a positive note" by striking a tone of convergence in the final communique.
A German official said the refugee issue was expected to be raised specifically at the leaders' dinner on Sunday night.
Turkey, which is hosting 2.2 million refugees from Syria, wants a concrete financial aid package from Europe in return for stemming the flow of migrants setting out from its shores to Europe.
"It's very difficult (on refugees) as the positions are very different from each other... though there will be a certain level of lip service on both sides," said Unluhisarcikli.
Sources said the final communique was expected to mention refugees, even if some countries did not see the G20 as the right forum for the discussion.
- Tax avoidance -
With the eurozone through the worst of its debt crisis, the economy will be less of an issue than at previous G20 meetings, although concern remains over the growth slowdown in China which could hurt emerging markets.
Leaders are also expected to give their assent to a final package of measures presented by the Organisation for Economic Cooperation and Development (OECD) to crack down on global tax avoidance.
Discussions on climate change will assume greater importance than usual coming just ahead of the UN COP21 conference in Paris that aims to agree a legally binding global climate treaty.
Campaigners will be hoping that a change of leadership in Canada and Australia -- whose previous premiers had shown scepticism about the climate drive -- will help encourage progress.
Meanwhile, any meeting between China's Xi Jinping and Japanese Premier Shinzo Abe will also be keenly watched over the tension in the South China Sea.
Other key guests at the summit include Saudi King Salman, whose delegation according to the Hurriyet daily has booked 546 hotel rooms at a cost of up to 15,000 euros ($16,115) each.