Adnan Pachachi, a member of the US-appointed Iraqi Governing Council (IGC) told Aljazeera on Thursday they were discussing ways to end the rebellion.
"We pledge to respect his honor and his security," said Pachachi.
Al-Sadr's loyalists and members of his militia, al-Mahdi Army, started an uprising against occupation forces on Sunday after Spanish forces opened fire on demonstrators in the southern city of Najaf, killing at least 20.
They were protesting at the occupation's detention of al-Sadr aide Mustafa al-Yacubi and the closure of a pro-al-Sadr publication.
Since then, more than 300 Iraqis and 33 US soldiers have been killed in fighting across Najaf, Karbala, Kut, Amara, Falluja, Ramadi, Baquba, Baghdad and Kirkuk.
US tanks and helicopters are reported to have attacked al-Sadr's office at dawn on Thursday in the Baghdad suburb of al-Sadr City.
Residents said tanks first opened fire on the office and then helicopters fired two rockets on it, reducing it to rubble. No one was hurt in the attack as there was no one inside the office at the time of attack.
US occupation forces vowed on Wednesday to "destroy" al-Mahdi army.
Al-Sadr’s office issued fresh vows to continue fighting the occupation after the attack on the office.
Al-Sadr's militia has proven to
be a potent force
"We had given orders for calm because we are peaceful people, and there were negotiations to calm the situation," said Amr al-Husayni, a spokesman for al-Sadr.
"But after they bombarded our headquarters and prayer room with Apache helicopters and tanks, we are ready to resume combat until the last drop of our blood," he told reporters.
Al-Sadr is reported to have taken refugee in a mosque in Najaf or the nearby town of Kufa.
Al-Husayni also told Aljazeera al-Mahdi militiamen were holding some Spanish troops hostage, a report the Spaniards categorically denied.
A US army general also denied reports of occupation forces being held captive in Najaf.
In Karbala, al-Sadr supporters issued an ultimatum on Thursday to occupation forces to withdraw from the holy city where a major religious commemoration is scheduled this weekend.
Polish troops are meeting with clerics in Karbala in an effort to ease tensions, said Polish army officials. However, they denied meeting al-Sadr representatives after the Shia cleric's supporters said they were negotiating with occupation officials.
Polish and Bulgarian troops battled al-Mahdi militiamen in Karbala overnight, leaving at least four Iraqis killed. There were no reports of casualties among occupation forces.
Thirty-three US soldiers have died
The United States rushed reinforcements to help Bulgarian troops in Karbala to deal with the escalating conflict there, said Bulgarian Foreign Minister Solomon Passi.
Lieutenant General Ricardo Sanchez admitted that Najaf and Kut were no longer under the occupation's control.
On Wednesday, Ukrainian occupation forces were forced to withdraw from the southern city of Kut after fierce fighting with militiamen.
Ten Iraqis were killed and 20 wounded in clashes on Wednesday in Najaf between occupation forces and al-Sadr supporters, reported hospital sources on Thursday.
Witnesses in Najaf, 160km south of Baghdad, reported fighting on Wednesday between al-Sadr supporters and Spanish and Ecuadoran forces in three neighbourhoods and the road leading north to Karbala.
Members of al-Mahdi Army militia opened fire with rocket-propelled grenades and automatic weapons on Polish and Bulgarian soldiers protecting the governor's office, a Polish military spokesman said.
Japanese under fire
In Abu Ghuraib, five US military vehicles came under attack, leaving them blazing on Thursday, but there were no reports of casualties.
Elsewhere, explosions were heard near a camp in southern Iraq where Japanese troops are based, but there were no reports of injuries among Japanese military personnel and nothing had landed in the grounds, said a Defence Ministry spokesman in Tokyo.
He said checks were being made into the explosions, which occurred during Wednesday night, but no further information was available.
Troops at the camp had sheltered in trenches within the grounds as a precaution.
Meanwhile, US troops killed an Iraqi policeman on Wednesday evening after soldiers opened fire randomly when they came under attack in Tikrit, about 160km north of Baghdad.