Najaf, Iraq, Jan 08 (Agencies): A powerful cleric whose fearsome militia once battled Americans urged followers on Saturday to resist the United States "with all means" in his first public address in Iraq after four years in exile.

Addressing a crowd of thousands, Muqtada al-Sadr said, "Let the whole world hear that we reject America. No, no to the occupier."

"We don't kill Iraqis… We target only the occupier with all the means of resistance."

A security agreement between Washington and Baghdad requires all US 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 US 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 honour 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.