BAGHDAD -- At the same spot where U.S. forces helped Iraqis topple a statue of Saddam Hussein in 2003, protesters yesterday tore down an effigy of President Bush and set it afire during a protest over plans to keep American troops in Iraq through 2011.

Demonstrators began arriving at central Baghdad's Firdos Square just after sunrise, some having walked hours across the capital. Most came from Sadr City, the stronghold of the Shiite Muslim cleric who called for the gathering, Muqtada al-Sadr.

The effigy of Mr. Bush, wearing a suit and tie and carrying a briefcase, dangled for hours as the crowd, which stretched for several city blocks, knelt in prayer and listened to clerics denounce the Status of Forces Agreement.

The pact, expected to be voted on in Iraqi's parliament next week, sets a Dec. 31, 2011, deadline for the withdrawal of U.S. forces from Iraq and requires U.S. combat troops to pull out of Iraqi cities, towns and villages by the end of next June.

But some people interviewed in the crowd insisted that the pact did not contain any withdrawal deadlines. Others said that whatever the pact said, they did not trust the U.S. or Iraqi governments to live up to it.

"They want to keep extending and extending," Bassim Hamoud said as he prepared to pass one of the Iraqi army checkpoints set up on the edge of the rally. "If there was a concrete time limit, we would go for it." Asked what he wanted that time limit to be for a U.S. withdrawal, Mr. Hamoud replied, "We want them to leave today."

Protesters' comments reflected both the lack of knowledge of the pact and the distrust many Iraqis feel toward their government and the Americans as a result of unmet promises since the U.S.-led invasion. At the time of the Saddam statue's toppling, most Iraqis were not expecting that nearly six years down the line, they still would be living in a city with spotty electricity, sewage running through the streets of their neighborhoods, military checkpoints choking traffic and bombs going off regularly.

Loyalists of hard-line anti-U.S. leaders such as Mr. Sadr say that if the Americans left, the violence would decrease, and Iraqis would be able to fix their own problems. As long as the United States has forces here, they say, Iraq never will be sovereign.

"They will not leave," said Abed Sahib Mohammed Hadi, an elderly, white-haired man. "If they wanted to leave, they would never have built those huge bases.

"We don't even know what's in the pact. It's never been presented to the people."

The pact has been explained to the public at least twice by Prime Minister Nouri al-Maliki, whose support propelled it through the Cabinet on Sunday and onto the floor of the parliament. Legislators loyal to Mr. Sadr tried to prevent the reading of the pact in the legislature, leading to a brawl in the chamber Tuesday and stalling debate.

If a vote is not held early next week, before a scheduled lawmakers' holiday, parliament could have trouble meeting a Dec. 31, 2008, deadline. That is when the U.N. mandate governing the presence of U.S. troops here expires. The new pact must be passed by then, or U.S. forces will have no legal basis for being in Iraq.

It is doubtful that opponents can muster enough votes in parliament to kill the pact. But their vocal opposition and yesterday's protest show that Mr. Maliki does not have the broad-based backing for the pact that he had sought.

Passing it by a thin margin would make it difficult to mend the political divisiveness that has hobbled Iraq's government. It also could give hard-line members of Mr. Sadr's Mahdi Army militia an excuse for resuming attacks on U.S. and Iraqi security forces after months of relative quiet.

"This is a normal consequence: more fighting," said Mohammed Ismael, 17, student from Sadr City and just the sort of young man ripe for recruitment into the Mahdi Army. "We are against this agreement, and we will resist it in any way we can."