Leaders of the world's 20 major economies (G20) have begun arriving in Antalya, a heavily guarded Turkish resort on the Aegean Sea coast, for a two-day summit, where the fight against violence is likely to eclipse economics.
The meeting is taking place in the shadow of the Paris assaults claimed by the Islamic State of Iraq and the Levant (ISIL) group which left at least 129 people dead and more than 350 others injured, 99 of them critically.
US President Barack Obama arrived on Sunday at the airport of Antalya, a holiday destination bristling with as many as 30,000 police and security personnel, to guard the G20 leaders.
Al Jazeera's Bernard Smith, reporting from Antalya, said security preparations for the summit is "the most intenstive security operation" Turkey has had to carry out.
"It's one of those rare occasions where so many leaders are gathered together in one event," he said.
French President Francois Hollande has cancelled his attendance at the summit, and is sending Laurent Fabius, the foreign minister, to represent him.
Although the G20 usually focuses on economic issues, the president of host country Turkey, Recep Tayyip Erdogan, has urged world leaders to prioritise the battle against ISIL, saying the attacks in Paris proved the time for words was now over.
Erdogan is expected to hold a one-on-one meeting with Obama later on Sunday.
The attacks in Paris prompted a worldwide alert and calls for a stepped-up offensive against ISIL.
The US already expects France to retaliate by taking on a larger role in the US-led coalition's bombing campaign against ISIL.
Obama is also seeking to persuade other European and Middle Eastern countries into more tangible steps to show their military commitment, a US official said before Obama embarked on his nine-day foreign trip.
The summit in Antalya brings Obama and fellow world leaders just 500km from Syria, where a four-and-a-half-year conflict has transformed ISIL into a global security threat and prompted Europe's largest migration flows since World War II.
Source: Al Jazeera and agencies