The Bush administration has said it would financially sanction any individual or organisation thought to be destabilizing Iraq.
A new executive order signed by the US President George W Bush, the US Department of Treasury and other government agencies on Tuesday will freeze financial assets belonging to people or groups that America believes to be "working to threaten stability in Iraq".
"All agencies of the US government are hereby directed to take all appropriate measures within their authority to carry out the provisions of this order," said the order.
The order did not name any person, company or group as such "de-stabilizer".
But the treasury department said it would draw up such a list "in coming weeks and months".
White House spokesman Tony Snow said the order would be targeting terrorist and insurgent groups, including those supported by Syria and Iran.