The Latest on the Syria summit in Istanbul (all times local):

8 p.m.

The leaders of Turkey, Russia, France and Germany have discussed the war in Syria at a summit, reiterating calls for a U.N.-backed political process to end the war that has killed hundreds of thousands of people.

A final statement Saturday from the four leaders also calls for the convening of a committee by the end of the year to work on constitutional reform as a prelude to free and fair elections in Syria. It also supports efforts to facilitate the "safe and voluntary" return of refugees to their Syrian homes.

The statement also rejects "separatist agendas aimed at undermining the sovereignty and territorial integrity of Syria as well as the national security of neighboring countries."

Many obstacles to a peace agreement remain. They include divided opinions about Syrian President Bashar Assad, who is backed by Russia and Iran. Western countries, meanwhile, condemn Assad for what they call indiscriminate attacks on civilians and Turkey has been helping insurgents trying to remove him from power.


12:40 p.m.

The leaders of Turkey, Russia, France and Germany are holding a summit in Istanbul to discuss security and humanitarian and political issues in Syria, hoping to lay the groundwork for eventual peace in a country devastated by years of war.

The leaders meeting Saturday afternoon are expected to promote the preservation of a cease-fire in Syria's northwestern province of Idlib. The agreement last month prevented a Syrian government offensive on the last rebel stronghold that many feared would have set off another refugee crisis.

Other discussion topics include access for humanitarian aid, early preparations for the drafting of a constitution and eventual reconstruction of the war-torn country.

Turkish President Recep Tayyip Erdogan is hosting Russian President Vladimir Putin, German Chancellor Angela Merkel and French President Emmanuel Macron.