A US mission in Iraq would be acceptable after year-end if a complete withdrawal were carried out and the US paid "compensation," radical Shiite cleric Moqtada al-Sadr said on Wednesday.

"It has been said that the weapons (Iraq is purchasing) are American, so the trainers should be American also," Sadr said in an address broadcast on Al-Masar television.

"We say that shall not happen unless a full withdrawal of the occupiers happens, and then a new agreement is signed after the payment of compensation," he added, without giving details of what he meant by compensation.

Sadr's remarks were his first public comments since returning to his movement's home base in the holy Shiite city of Najaf in southern Iraq on Monday.

The cleric moves between Najaf and the Iranian city of Qom, where he is apparently pursuing religious studies.

The statement from Sadr comes with Washington and Baghdad at an impasse over negotiations for a future US military presence in Iraq.

American officials have conditioned any post-2011 mission on their troops having immunity from prosecution, but Iraqi leaders have said such protections are unnecessary.

"We still object to the American presence in Iraq," Sadr said in his Wednesday address. "We consider it an occupation. Keeping American trainers in Iraq is part of that."

Last month, Sadr ordered his followers not to launch attacks on US troops before a year-end deadline for their pullout. American forces have accused militias linked to the cleric of largely being behind attacks on its soldiers.

Sadr's bloc holds five cabinet posts and has 40 seats in parliament.