The national conference on Iraq's future is going into an unscheduled fourth day as delegates hammer out the shape of the first post-war parliament.
Fighting has continued in Iraq during the conference
They are due to select an interim assembly which will monitor the country's move to democracy ahead of direct elections next year.
The conference is also pursuing efforts to end the armed stand-off in Najaf.
Shia cleric Moqtada Sadr refused to meet delegates from Baghdad, but they say they aim to return shortly.
Mr Sadr declined to receive the six-member team on Tuesday, citing concerns about his security and their status. Aides said he regarded them as messengers rather than negotiators.
It was a high-risk venture for the delegates, who flew to Najaf by US military helicopter and then drove through the old city to the Imam Ali shrine, where Mr Sadr is holed up.
Conference aims to choose an Interim National Council of 100 members
The council will oversee, advise and question government policy
National Council can veto orders or decrees from the Council of Ministers by a two-thirds majority
National Council can appoint replacements to the presidency in the event of death or resignation and can approve budgets
Nevertheless, Iraqi religious and political leaders say the visit itself was a positive development and one delegate said they would return to Najaf in the coming days.
The governor of Najaf, Adnan al-Zurufi, has told the BBC that Mr Sadr would be welcome to join the political process if his forces laid down their arms.
But he said he thought the fighting would continue since Mr Sadr, as he put it, only seemed to understand military methods.
The BBC's Kylie Morris, reporting from Najaf, says the cleric remains in a strong position, with Shia Islam's holiest site under the rule of his militia and US-led forces reluctant to cause any damage, aware of the negative repercussions that would prompt.
Sporadic shooting was reported in the city on Wednesday morning.
In other developments:
- a US marine is killed in action in the largely Sunni Muslim province of al-Anbar, west of Baghdad, and one UK soldier is killed and one injured in Iraq's second city, Basra
- the Pentagon suspends a decision to withhold some payments to Halliburton, its biggest contractor in Iraq, over an army supplies dispute
Delegates in Baghdad have yet to decide who will serve on the 100-seat interim assembly, and there has been confusion over how assembly members will be chosen.
They were originally scheduled to vote on a single slate of 81 nominees which would have needed the support of 65% of the delegates to be selected.
But, following objections from smaller political groups, delegates are now expected to vote on competing slates.
The remaining 19 seats are due to be filled by former members of the US-appointed Iraqi Governing Council, who were not included in the interim government after the transition in June.
Ibrahim Nawa, an adviser to the United Nations mission in Iraq, said the fact that the national conference was taking place at all was important.
"After almost four decades, Iraqis can gather and speak and can decide the government and differ with each other and accept the differences," he said.