Tens of thousands of Iraqi Shia Muslims have protested against US plans for the handover of power.
The mass turnout sends a clear message to the coalition
The march past the main mosque in the southern city of Basra was peaceful, but the BBC's Dumeetha Luthra says it was a display of latent power.
The Shias, who are the majority of Iraqis, do not want to be marginalised as they were under Saddam Hussein.
Iraq's leading Shia cleric, Grand Ayatollah Ali Sistani, has called for direct elections later this year.
The coalition says early elections are not feasible, and proposes an appointed government broadly representing Iraq's diverse religious and ethnic groups.
The demonstrations in Basra, Iraq's second city, were called for by the city's clerics and show the strength of
local leader Ayatollah Saeed Ali Hakim, says our correspondent.
It sends a clear message to the Americans, she says - we can mobilise the people against you if we need to.
Speaker after speaker called for the rejection of the US plans and demonstrators chanted and sang in support of their leaders, shouting "No, no to America, yes, yes to Sistani."
Armed members of the Shias' own private militia were in evidence, but the British armed forces who control the southern zone of Iraq kept a low profile.
Shias were oppressed under Saddam Hussein and had been expected to be strong supporters of the US-led coalition which overthrew the old regime.
While the Shia-dominated southern areas controlled by the British military have seen far less unrest than in the so-called Sunni Triangle around Baghdad, the Basra protest shows their support is not unconditional.
Correspondents say problems arose after an agreement in November between the interim Iraqi Governing Council and US administrator Paul Bremer that a new Iraqi assembly to take power by the middle of the year would be selected, not elected.
Shia concerns are that the selection process by regional caucuses of "notables" will ensure representation of minority groups such as the Sunnis and the Kurds from the north, possibly at the expense of the Shias.
Direct elections with some form of proportional representation would give power to the Shia majority, but Mr Bremer says Iraq's war-torn infrastructure simply could not support general elections by the desired transfer deadline of 30 June.
Yet our correspondent says that the problem for the Americans remains that an Iraqi government would have no legitimacy without Shia backing.
Also in dispute is the role that the United Nations should play in Iraq, and whether the status of US forces in Iraq should be subject to approval by any transitional authority.
The Coalition Provisional Authority is set to meet the UN Secretary-General Kofi Annan on 19 January.
Commentators say it is hoping Mr Annan will use the opportunity to send a clear message to Ayatollah Sistani that democratic elections will not be possible before the end of June.