A powerful cleric whose fearsome militia once battled Americans urged followers Saturday to resist the United States "with all means" in his first public address in Iraq after four years in exile.

Addressing an adoring crowd of thousands, Muqtada al-Sadr also called on the newly formed government of Prime Minister Nouri al-Maliki to make sure all U.S. forces leave Iraq by the end of the year as planned. And he warned that "we have the political means" to reject that government if it does not provide security and services to its citizens.

The fiery Shiite cleric, who abruptly returned from Iran earlier this week, whipped the crowd into a frenzy when he called the U.S., Israel and Britain "our common enemies."

But he reserved his harshest comments for the U.S., his primary foe, which invaded Iraq in 2003.

"Let the whole world hear that we reject America. No, no to the occupier," al-Sadr said during his 35-minute speech. "We don't kill Iraqis — our hands do not kill Iraqis. We target only the occupier with all the means of resistance."

A security agreement between Washington and Baghdad requires all U.S. forces to be out of Iraq by the end of the year. Although both al-Maliki and the Obama administration have maintained the roughly 50,000 U.S. troops will leave by then, officials in both nations have acknowledged that Iraq is not yet ready to protect its borders from possible invasion. That's led to widespread speculation that al-Maliki ultimately will ask a small number of American forces to remain. .

"The new government must work to get the occupier out of the country, in a suitable way," al-Sadr said. "We heard a pledge from the government in this regard, and we are waiting for it to honor its word."

Al-Sadr, 37, left Iraq in 2007 for Iran, fleeing arrest in the killing of another cleric. It is unclear how long he'll stay here.