Lieutenant General Ali Ghaidan, the Iraqi commander in charge of the operation, said he expected the whole area to be secured by today. There were no immediate reports of casualties in the Basra fighting.
A full-blown uprising by Sadr, who led two rebellions against US-led forces in 2004, could lead to a dramatic increase in violence in Iraq at a time when the Sunni extremist group Al Qaeda in Iraq appears poised for new attacks after suffering severe blows last year.
At least 14 people were killed and 84 wounded in yesterday's fighting in Sadr City, the Baghdad stronghold of Sadr's Mahdi Army, officials said. Sporadic clashes were continuing after sundown.
The battles in Sadr City and the crackdown in Basra are part of a government campaign against followers of Sadr and Iranian-backed Shi'ite splinter groups the United States has identified as the gravest threat to a democratic Iraq.
Prime Minister Nouri al-Maliki, also a Shi'ite, has ordered Sadr to disband the Mahdi Army, Iraq's biggest Shi'ite militia, or face a ban from politics.
In the statement, Sadr lashed back, accusing the government of selling out to the Americans. Sadr, who is believed to be in Iran, said he had tried to defuse tensions last August by declaring a unilateral truce, only to see the government respond by closing his offices and "resorting to assassinations."
"So I am giving my final warning . . . to the Iraqi government . . . to take the path of peace and abandon violence against its people," Sadr said. "If the government does not refrain . . . we will declare an open war until liberation."
At a news conference, Iran's ambassador to Baghdad said that his government supports the Iraqi move against "lawbreakers in Basra" but that the "insistence of the Americans to lay siege" to Sadr City "is a mistake."
"Lawbreakers [in Basra] must be held accountable . . . but the insistence of the Americans to lay siege to millions of people in a specific area and then bombing them randomly from air and damaging property is not correct," Ambassador Hassan Kazemi Qomi said.
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