Syria is expected to be high on the agenda for conference that Baghdad last hosted in 1990 after invading Kuwait.
A series of bombings in the Iraqi capital has struck a crowded restaurant, a police patrol and the homes of two policemen, killing at least 13 people and wounding 36, officials say.
In northwest Baghdad, a parked car exploded outside a crowded restaurant in the Shia neighbourhood of Shula, killing ten people and wounding 25 others, police officials said.
A police first lieutenant said the car was driven by a suicide attacker.
Naseer Ali, owner of a grocery shop in Shula, said he was about 150 metres from the restaurant when the blast went off.
Ali said he and other witnesses rushed to help the victims until the ambulances arrived.
“I was in my shop when I heard a powerful explosion and everybody rushed to the explosion site,” he said.
“Part of the restaurant was damaged and the windows of the nearby shops were shattered. We saw several wounded people screaming for help.”
Earlier on Thursday, explosions hit two adjacent homes of Baghdad policemen in the predominantly Sunni neighbourhood of Amariyah, killing two and wounding several people, among them three children. It was not clear if the two policemen were among the casualties.
Another bomb attack targeted a police patrol in Baghdad, killing a policeman and wounding three officers.
Violence in Iraq has declined dramatically since its peak in 2006 and 2007, but attacks remain common, especially in Baghdad. A total of 126 Iraqis were killed in violence in April, according to official figures.