"No, No, to America! No, No to the devil!"shouted crowds of men, women and children as they walked through the streets of Sadr City towards Mustansiriya Square, a distance of about three kilometres.
A message from al-Sadr, reported to be in Iran, was read out at the protest by Sheikh Abdul-Hadi al-Mohammadawi, his aide, calling on the Iraqi parliament to reject a US-Iraqi security pact that would extend the presence of American forces in Iraq.
Al-Sadr said that anybody who claims the agreement will end "the occupation of our land," or "tells you that it gives Iraqi sovereignty is a liar".
He also said that the deal "will stigmatise Iraq and its government for years to come".
|US and Iraqi officials have a December 31 deadline for reaching a security agreement [EPA]
The public show of opposition comes as US and Iraqi leaders near a December 31 deadline to reach agreement on the deal.
An agreement on a draft security deal has reportedly been reached, which would govern the future status of US forces in Iraq after the present UN mandate ends in December.
But the pact has still to be approved by leaders of both countries.
Details have not been made public.
A point of contention in the months-long negotiations has been whether US troops and contractors would fall exclusively under US jurisdiction if accused of serious crimes in Iraq.
Robert Gates, the US defence secretary, said on Friday in Washington that US military leaders "are all satisfied that our men and women in uniform serving in Iraq are well protected".
Bahraini official's visit
In other news, Bahrain's foreign minister arrived in Baghdad on Saturday for a one-day visit. Bahrain named a new ambassador to Iraq last month.
The Iraqi foreign ministry said Sheikh Khalid bin Ahmed Al-Khalifa will hold talks with his Iraqi counterpart, Hoshyar Zebari.
More senior Arab politicians and diplomats have started to visit Iraq in a sign of increasing ties between Iraq and its neighbours.
Three years ago, Bahrain's high-level envoy in Iraq, Hassan Malallah al-Ansari, was wounded when attackers tried to abduct him on his way to work in Baghdad.