The leaders said they would cooperate with the experts and still hoped to join Shi'ites and Kurds in a grand coalition government, which could take several months to be formed.
The Iraqi Electoral Commission (IECI) has invited two Arab League representatives, a Canadian politician and a European academic to Baghdad to review the disputed results.
Their presence could help bring disgruntled Sunnis on board.
The Iraqi Islamic Party, part of the main Sunni bloc, gave the initiative a cautious welcome.
"The arrival of this committee shows the international community has responded to our demands," said party official Iyad al-Samarraie.
But some electoral officials said the move was a face-saving bid that would allow some Sunnis and secularists to back down from demands for a vote rerun without alienating their supporters.
Partial but near-complete counts show the Shi'ite Islamist coalition, which forms the backbone of the present government, should have nearly half the seats in the new parliament.
Petrol queues
Efforts to resolve the standoff came amid chaos created by the closure of a major oil refinery over fears of insurgent attacks - prompting long queues for fuel in the capital Baghdad.
“If the refinery stays shut, the queues at fuel stations will get longer and I imagine I can see I'll have to wait more than three hours for petrol," taxi-driver Sadiq Shamikh said.
Deputy Prime Minister Ahmad Chalabi has taken over direct control of the powerful oil ministry against the will of the incumbent minister Ibrahim Bahr al-Uloum, officials confirmed.
A ministry spokesman allied to Bahr al-Uloum said the country was facing an oil supply crisis. "Production in the north, centre and south is about to suffocate," he said.
Iraq's largest oil refinery, in Beiji, was shut down on December 18 because of the deteriorating security situation.
Prisons overcrowded
In a separate development, a senior US commander said inspections of two Iraqi-run jails, prompted by the recent discovery of a bunker packed with mistreated prisoners, found overcrowding and signs of prisoner abuse.
Iraqi and American inspectors made the new findings at a Baghdad facility on December 20 and one in Tal Afar on Wednesday, a US military official said.
The findings suggest broader problems at Iraqi-run detention facilities as the US military takes steps towards turning over thousands of detainees to the Iraqi government.
"While there were overcrowded conditions, there were no signs of recent abuse," said Major General William Webster, who commands a 30,000-strong force responsible for security in Baghdad.
"There were detainees who talked about having been abused before, and some of them showed signs of that," he said.
Major Webster did not describe these signs of abuse. He said a committee of Iraqi government and US officials was continuing its investigation and inspections of Iraqi jails.
A raid by US forces last month at a secret Baghdad bunker found 173 men and teenage boys held by the Interior Ministry, many malnourished, beaten and showing signs of torture.
The Iraqi government earlier in December said 13 prisoners at another Interior Ministry prison also showed signs of abuse.
The US military said this week it was holding 14,600 detainees in Iraq.
Officials said there was no timetable for turning over detention facilities to the Iraqis, but it would not be done until
Iraqi forces met standards of care and custody laid out in international law.
And the Australian newspaper reported on Friday that an Australian man who travelled to Iraq to marry his cousin and was detained in the notorious Abu Ghraib prison for two years without charge for "security reasons" has been released by the US military.