KARBALA, Iraq -- A visitor need not go far or search hard to hear and see the anti-American venom that bubbles through this ancient shrine city, which once welcomed U.S. forces as liberators.
"The American ambassador is the gate through which terrorism enters Iraq," says a banner hanging from the fence surrounding the tombs of Imam Hussein and Imam Abbas, among the most revered martyrs of the Shiite Muslim faith.
A song screeches from a boombox at a nearby CD shop: "If the occupiers come at us, we will plant a bomb underneath them."
For three years, most of Iraq's Shiites welcomed -- or at least tolerated -- the U.S. presence here. In the weeks immediately after the American-led invasion, the mothers and sisters of Saddam Hussein's Shiite victims clutched clumps of dried earth as they wept over mass graves and thanked God for ending their oppression.
The Shiite acceptance of an American presence allowed troops to concentrate on putting down the insurgency in western Iraq, which is led by Sunni Muslim Arabs. With the exception of an uprising in mid-2004 by followers of radical cleric Muqtada Sadr, the south has been relatively quiet and peaceful under the sway of Grand Ayatollah Ali Sistani.
But now the mood has shifted. Perceived American missteps, a torrent of anti-U.S. propaganda and a recently emboldened Shiite sense of political prowess have coalesced to make the south a fertile breeding ground for antagonism toward America's presence.
The change has weakened the Bush administration's position and dimmed its hopes that Iraq's Shiites would counter the vehement anti-Americanism of their coreligionists across the border in Iran.
"There is an anger," said Jaffar Mohammed Asadi, spokesman for Ayatollah Mohammed Taqi Modaressi, a moderate and well-regarded cleric known more for his attempts to boost business in Karbala than for fiery anti-American speeches.
"You can hear it in the slogans at Friday prayers: 'Death to America,' " he said. "They're burning American flags. They're saying, 'The Americans won't leave except by the funerals of their sons.' "
Several factors have combined to produce that Shiite fury.
Many Shiites think the U.S. betrayed them in 1991 when then-President George H.W. Bush called on Iraqis to rise up against Hussein but then took no action as the dictator mowed down an uprising in the south.
Moreover, nationalism is a strong current among Iraqi Shiites, and analysts say their anti-Western attitudes were sure to surface some day.
"We had a lot of grace period," said Graham E. Fuller, a former Mideast-based CIA operative now writing books about the region. "But essentially, no group in Iraq that aspires to rule with legitimacy can act in a way perceived as being pro-American."
Above all, however, the new Shiite attitude reflects the changed political reality of Iraq's south: Once the Shiites were weak; now they have power. Many say they no longer need the Americans.
In and around Karbala and Najaf -- the southern Iraqi cities that house the holiest shrines of Shiite Islam -- dozens of checkpoints are staffed by Shiite police officers and soldiers. The security has made the south much safer than Baghdad or heavily Sunni provinces. As U.S. forces struggle to recruit police officers and soldiers in Sunni areas, police in the southern Iraqi province of Muthanna on Wednesday proudly announced that they had busted a ring of drug dealers after a two-hour shootout.
"We agreed with Americans only at the point of removing Saddam Hussein," said Sheik Abu Mohammed Baghdadi, a cleric in Najaf who is close to Sistani. "The relationship ended at that point."
U.S. officials point to yet another factor in the souring of relations: what they describe as an intense propaganda campaign, some of which emanates from Iran, that seeks to paint American policy in the ugliest terms.
In interview after interview in Najaf and Karbala, Shiites adhered to a version of current events that magnified corruption and torture cases into pervasive abuses by the Americans and depicted U.S. Ambassador Zalmay Khalilzad, a Sunni born in Afghanistan, as anti-Shiite.
"We need to do a better job of explaining what we're doing, and some people are intentionally trying to mislead," Khalilzad said in a recent interview.
Beyond the propaganda war, however, there is a clash between the culture of the American military and the pious, rural values of Iraqi Shiites.
Akeel Mahmoud Qazali, the governor of Karbala province, said he had lambasted his American counterparts after U.S. soldiers brought explosives-sniffing dogs into the provincial headquarters before the arrival of a visiting American delegation in February. Dogs are considered unclean by observant Muslims.
In Najaf last month, Iraqi officials looked on with shock as bored American soldiers flung pieces of bread at one another.
"They're playing with food," one police officer said with disgust. "That's a sin."
And Shiites bridle at what they see as American and British interference in matters of state -- especially security.
"Beside every Cabinet minister there is an American advisor," said Mohammed Bashar Najafi, son of, and spokesman for, one of Iraq's four grand ayatollahs. "Each province has an American advisor. Each city council has an American advisor. The country is occupied, and this occupation is a weight on the chest of Iraq."
Provincial officials in Basra and Amarah, as well as here in Karbala, have had recent run-ins with American and British military counterparts. Basra's government for a time completely suspended contacts and cooperation with British troops.
In Karbala, "the American soldiers are wandering the streets asking people provocative questions about whether they belong to this militia or that," said Qazali, the governor. "They've been doing airborne raids without the knowledge of security forces in ways that are terrifying local residents."
Shiites bristle at the Americans' refusal to let them take on insurgents the way they'd like to. They say their hands are bound by U.S. forces and Khalilzad, who has made a priority of reforming Iraq's internal-security forces, which are dominated by sectarian militias.
Sunnis, who feel they have been targeted by the security police, have applauded those American initiatives; Shiites are outraged. The latter see the move against the militias as a ploy to disarm Shiites in the face of insurgent attacks.
One banner hanging from a government building in Karbala said the blood of Iraqi Shiites "stained the hands of Khalilzad" along with those of his Sunni Arab "deputies."
"Americans are interfering and not allowing us to control security," said Fallah Aliyawi, a publisher in Najaf. "Iraqis know better how to enforce security."
Despite the tensions, few believe southern Iraq is on the verge of an explosion. Deadly attacks against U.S., British and allied troops in the region appear to have increased in recent weeks, but the U.S. military says assaults there on allied forces still average less than one a day except in Basra, which has about two a day.
Any call to violent jihad, or holy war, Shiites say, would come only from the senior level of the clergy, the marjaiyah, as it did in the 1920s, when Shiites here rose up against Iraq's British occupiers. For now, the clergy is watching and waiting, perhaps convinced that it will get what it wants without having to sacrifice more Iraqi blood.
"The marjaiyah is calculating things and counting things according to the benefit of the Iraqi street," said Najafi, a mid-ranking cleric. "It wants independence with a minimum of losses and a maximum of profit. The marjaiyah has not ruled out the option of calling for jihad, and the Americans and their allies best not forget that."
Special correspondents Othman Ghanim in Basra and Hassan Halawa in Samawah, Iraq, contributed to this report.