The meeting was originally scheduled to start on Friday, but had been indefinitely postponed for unspecified "emergency reasons," a statement said.
The postponement reflected the effect the worsening violence has had on efforts to stabilise the government and end the bloodshed.
The delay had threatened to damage the government of Nuri al-Maliki, the prime minister, which took office just over four months ago vowing to implement a 24-point national reconciliation plan.
Wednesday's statement said the conference was postponed because of organisational problems, denying media reports suggesting the delay was caused by disputes over the gathering.
Al-Maliki, the head of what is formally termed a national unity government, presented the national reconciliation plan within days of taking office in May, but has been unable to effectively implement any of its stipulations.
In continuing violence in Iraq, a roadside bomb killed a provincial police intelligence chief in the south of the country early on Wednesday, police said.
The bomb, planted on the main road between the cities of Amara and Basra, killed Ali Qassim al-Tamimi, and four bodyguards, Maysan police said.
Elsewhere, local Sunni and Shia leaders met in an attempt to resolve the fate of more than 40 people missing since their 13-car convoy was stopped at a checkpoint on Sunday outside Balad, where almost 100 people were killed in five days of sectarian fighting.
Police said the hijacked cars had been diverted to the nearby Shia area of al-Nebaiyi on Balad's outskirts.