The Iraqi city of Falluja is waiting to see whether a ceasefire to end fighting between Sunni Muslim fighters and US forces will take effect.
The US began its offensive in Falluja on Monday
A team from the US-appointed Iraqi Governing Council has said a 12-hour ceasefire was due to begin at 0600GMT.
The US-led coalition in Iraq would not confirm the ceasefire, saying it could not comment on any negotiations.
UN Secretary-General Kofi Annan urged both sides to show restraint and avoid civilian casualties.
Mr Annan's spokesman Stephane Dujarric said in a statement that the secretary-general was following developments in Iraq "with great anxiety".
Meanwhile the deadline given by kidnappers of US civilian Thomas Hamill, who threatened to kill him unless US troops ended the Falluja operation, passed with no indication as to whether or not he was still alive.
Earlier Australian TV showed pictures of Mr Hamill taken hostage by fighters outside Baghdad after an attack on a convoy taking fuel to US troops.
Another group who kidnapped three Japanese civilians have reportedly said they will release their hostages on Sunday.
The US-led coalition has not commented on reports that it will also observe the ceasefire in Falluja.
Iraqi negotiator Qahtan al-Rubaie said the ceasefire call in Falluja was being issued by tribal, religious and community leaders in the town.
He was speaking after the delegation returned to Baghdad and met US officials, including Washington's administrator in Iraq, Paul Bremer.
Noriaki Imai, 18, Japanese researcher
Nahoko Takato, 34, Japanese aid worker
Soichiro Koriyama, 32, Japanese photojournalist
Nabil George Razuq, 30, Palestinian aid worker
Fadi Ihsan Fadel, 33, Canadian aid worker
Thomas Hamill, 43, US civilian worker
He told Reuters news agency it was hoped that the ceasefire would open the way for talks on a possible withdrawal from Falluja by US marines.
However, another member of the Governing Council, Mahmoud Othman, expressed doubts that the ceasefire would actually take effect.
"Fighters in (Falluja) say they want the Americans to withdraw, but I don't know how likely that is," he told the Associated Press news agency.
US Brig Gen Mark Kimmitt, deputy head of coalition operations, had said earlier that if the talks did not bear fruit, US forces would resume offensive operations.
Hundreds of civilians are reported to have been killed in Falluja.
Reports from Falluja say food and medical supplies are low
The US began its offensive against Sunni insurgents there on Monday, in an effort to "pacify" the town where four civilian security contractors were killed and mutilated last week.
But the IGC, reportedly furious that it was not consulted, called for an end to the fighting.
On Saturday, Gen Kimmitt called on the insurgents to lay down their arms and hand over the people who were responsible for the killing of the contractors.
The US has reported the deaths of at least 42 of its soldiers in combat since last Sunday in Iraq.
Several parts of Baghdad saw fighting on Saturday, as gunmen armed with rifles and rocket-propelled grenades roamed the streets launching hit-and-run attacks on US patrols.
Attacks also continued on US convoys on the western outskirts of Baghdad.
Further south, American helicopter gunships bombarded rebel positions outside the town of Kut, in what US forces called a mopping-up operation. On Friday, they said they regained control of the city.
As concern grew over hostage-taking by insurgents in Iraq, the Arab satellite television channel al-Arabiya broadcast a videotaped message from a previously unknown group threatening to kill 30 hostages it claimed to be holding.
The group of eight masked men identified themselves as the Brigades of the Hero Martyr Sheikh Ahmed Yassin, after the Palestinian militant cleric assassinated by Israel last month.
They called for the withdrawal of coalition forces, saying their hostages included Japanese, Bulgarians, Israelis, Americans, Spaniards and Koreans.
However, no hostages were seen on the tape and there was no way to verify the group's claims.