The anti-American cleric Moqtada al-Sadr has told his followers to stop attacking US troops in Iraq so as not to slow their withdrawal from the country.

In a statement posted on his website, the Shia cleric tells his militias to halt attacks until the US withdrawal is finished at the end of the year as required under a security agreement between Washington and Baghdad.

"Out of my desire to complete Iraq's independence and to finish the withdrawal of the occupation forces from our holy lands, I am obliged to halt military operations of the honest Iraqi resistance until the withdrawal of the occupation forces is complete," al-Sadr said in the statement, posted on Saturday night. Sadrist lawmaker Mushraq Naji confirmed the statement on Sunday.

However, al-Sadr warned that "if the withdrawal doesn't happen ... the military operations will be resumed in a new and tougher way." The statement followed last week's announcement by US officials in Baghdad of the start of the withdrawal of some 45,000 US military personnel from Iraq. However, US and Iraqi leaders are considering whether some American troops should remain past the 31 December deadline as Baghdad continues to struggle with instability and burgeoning influence from Iran. Last month, Iraqi leaders began negotiating with US officials to keep at least several thousand troops in Iraq to continue training the nation's shaky security forces.

Officials in Washington say President Obama is willing to keep between 3,000 and 10,000 US troops in Iraq. But prime minister Nouri al-Maliki and parliament still have not indicated how many US troops Iraq might need or how long they would stay.After more than eight years of war, many weary Iraqis are ready to see US troops go, and staunchly defend their national sovereignty against an American force they see as occupiers.

Al-Sadr's followers vehemently oppose a continued US military presence in Iraq, and walked out of last month's meeting where political leaders decided to open the talks on having American troops stay.

"Our goal has been always to fight the occupiers because they are still in our country," Naji said on Sunday.

Other Iraqi officials privately say they want American troops to continue training the nation's security forces for months, if not years, to come. The president of Iraq's northern Kurdish region this week pleaded for US forces to stay to ward off threats of renewed sectarian violence. Many Iraqis – Sunnis and Shias – share that fear.

"As for me, and the sheiks of Nasiriyah, we want the US Army to stay," Sheikh Manshad al-Ghezi of the southern Shia city of Nasiriyah said in a recent interview. "We are afraid of civil war. All the parties and groups in Iraq are armed and the Iraqi Army cannot manage to bring security to Iraq and stop the fighting among these parties."