BELEK, Turkey (Reuters) - U.S. President Barack Obama arrived in Turkey on Sunday for a summit of world leaders that has taken on a sense of urgency following deadly Paris attacks that pushed the fight against Islamic State militants to the top of the agenda.

Obama, who called the Paris attacks "an outrageous attempt to terrorize civilians" on the eve of his departure, faces the question of how the West should respond now that it has become clear that Islamic State poses a threat far beyond its militant strongholds in Syria and Iraq.

Washington already expects France to retaliate by taking on a larger role in the U.S.-led coalition’s bombing campaign against Islamic State.

But Obama also seeks to coax other European and Middle Eastern countries into more tangible steps to show their military commitment, a U.S. official said before the president embarked on his nine-day foreign trip.

It remains to be seen, however, whether the United States itself has an appetite for much deeper involvement after already stepping up air strikes and committing small numbers of special operations troops to northern Syria to advise opposition forces in the fight against Islamic State.

The two-day summit of the Group of 20 major economies brings Obama and fellow world leaders just 500 km (310 miles) from Syria, where a 4-1/2-year conflict has transformed Islamic State militants into a global security threat and spawned Europe's largest migration flows since World War Two.

The coordinated attacks by gunmen and suicide bombers in Paris on Friday puts Obama and other leaders of the Group of 20 major economies under increased pressure to find common cause.

At least 127 people were killed in attacks on a concert hall, restaurants, bars and a sports stadium.

Obama was due to hold bilateral talks with Turkish President Tayyip Erdogan before the start of the summit and later, at a working dinner with fellow leaders, to have in-depth discussions on Syria, ranging from counter-terrorism to the refugee crisis.